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GASOLINE  AUTOMOBILES 


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GASOLINE  AUTOMOBILES 


BY 

JAMES  A.  MOYER 

Director  of  University  Extension,  Massachusetts  Department  of  Education; 

formerly  Junior  Professor  of  Mechanical  Engineering  in  the.  University 

of  Michigan.    Member  of  Society  of  Automotive  Engineers, 

and   American    Society    of    Mechanical    Engineers; 

formei  ly  member  of  Standards  Committee  of  the 

Society  of  Automobile  Engineers. 


FIRST  EDITION 
SECOND  IMPRESSION 


McGRAW-HILL   BOOK   COMPANY,  INC. 

NEW  YORK:  370  SEVENTH  AVENUE 
LONDON:  6  &  8  BOUVERIE  ST.,  E.  C.  4 

1921 


COPYRIGHT,  1921,  BY  THE 
McGRAW-HILL  BOOK  COMPANY,  INC. 


PREFACE 


THE  purpose  of  this  book  is  to  present  clearly,  briefly, 
and  interestingly  the  essential  principles  of  automobile  con- 
struction and  operation.  It  is  expected  to  furnish  practical 
help  to  drivers  who,  when  faced  by  ordinary  operating 
troubles,  want  to  know  how  to  locate  the  cause  and  apply 
the  remedy. 

Ordinarily  an  owner  wishes  to  know  first  of  all  the  uses 
of  the  numerous  parts  of  his  automobile,  so  that  he  may 
anticipate  repairs  and,  when  repairs  actually  become  neces- 
sary, he  may  know  where  to  begin  repair  work,  and  whether, 
once  done,  such  work  is  right  and  the  charges  therefor  are 
reasonable. 

Because  of  the  increasing  cost  of  materials  and  services 
there  is  a  growing  tendency  among  owners  to  keep  auto- 
mobiles for  several  seasons.  There  is,  therefore,  more  incen- 
tive than  formerly  to  keep  automobiles  in  good  repair.  Auto- 
mobiles generally  deteriorate  more  because  of  lack  of  care 
and  attention  than  from  actual  use.  Much  of  this  deteriora- 
tion is  due  to  ignorance  and  the  consequent  failure  to  pre- 
vent the  kind  of  wear  which,  if  not  corrected,  will  lead  to 
heavy  expenses  for  repairs. 

As  the  cost  of  repairs  has  greatly  increased  of  late  be- 
cause of  labor  charges,  automobile  operators  are  becoming 
interested  in  finding  ways  of  decreasing  ordinary  as  well 
as  extraordinary  running  expenses.  They  want  to  learn 
how  to  get  the  last  unit  of  power  from  a  gallon  of  gasoline 
and  how  to  exact  the  greatest  possible  mileage  from  an  auto- 
mobile before  it  is  exchanged  for  a  new  one. 


vi  PREFACE 

A  book  prepared  with  these  objects  in  view  should  also 
be  suitable  for  general  scientific  study,  if,  of  course,  the 
theory  is  accurate  and  carefully  explained.  Such  a  book 
will  give  information  that  will  be  most  useful  to  students 
of  automotive  engineering,  whose  schooling,  obviously, 
should  not  deal  too  much  with  minor  details  of  automobile 
equipment. 

Many  books  on  this  subject  are  really  catalogs  of  details, 
and  books,  if  at  all  complete,  must  be  of  unwieldy  size  and 
include  many  dry  and  uninteresting  data.  The  author  be- 
lieves that  there  is  a  demand  for  a  readable  book  devoted 
only  to  essentials.  For  example,  not  all  types  of  carbureters 
and  ignition  devices  will  be  explained,  but  considerable 
space  will  be  devoted  to  the  explanation  of  the  principles 
underlying  commonly  used  equipment  and  systems.  In  the 
description  of  carbureters  a  series  of  symbols  has  been 
adopted  which  should  make  it  easy  to  understand  any  type 
mentioned  after  the  careful  study  of  one  type.  Only  limited 
space  has  been  given  to  the  subject  of  magnetos  because 
their  use  on  automobiles,  except  on  trucks,  is  rapidly  de- 
creasing in  favor  of  simple  battery  systems  of  ignition. 

The  author  is  especially  indebted  to  his  brother  J.  C. 
Moyer,  consulting  mechanical  engineer,  of  Philadelphia,  for 
the  preparation  of  portions  of  many  chapters.  Special 
acknowledgment  is  also  due  to  J.  C.  Vincent,  Past-President 
of  Society  of  Automotive  Engines  and  Vice-President  of  the 
Packard  Motor  Car  Company,  to  Charles  W.  Hobbs,  Herbert 
A.  Dallas,  agents  of  the  Massachusetts  Division  of  Univer- 
sity Extension,  and  to  Arthur  E.  Ashworth,  Miss  Betsy 
McCausland,  and  Herbert  S.  Eames,  instructors  in  the  same 
Division. 

JAMES  A.  MOYER. 

Boston,  Mass., 
March,  1921. 


CONTENTS 


PREFACE  v 

CHAPTER  PAQE 

I  AUTOMOBILE  TYPES  AND  PARTS 1-20 

II  AUTOMOBILE  ENGINES    21-  48 

III  GASOLINE  AND  SUBSTITUTES 49-  62 

IV  GASOLINE  CARBURETERS  63-103 

V  AUTOMOBILE  IGNITION   104-147 

VI  MAGNETOS  AND  IGNITION  TESTING 148-166 

VII  ELECTRIC   STARTERS    167-183 

VIII  CLUTCHES,  TRANSMISSIONS  AND  DIFFERENTIALS  184-222 

IX  LUBRICATION  AND  COOLING  SYSTEMS 223-246 

X  AUTOMOBILE  TROUBLES  AND  NOISES 247-256 

INDEX   .  257 


GASOLINE  AUTOMOBILES 


CHAPTER  I 
AUTOMOBILE  TYPES  AND  PARTS 

THE  purpose  of  this  book  is  to  give  such  information 
about  the  construction  and  maintenance  of  automobiles  that 
inexpert  owners  can  make  the  simpler  adjustments  and 
repairs  intelligently  and  economically.  The  average  man 
is  becoming  more  and  more  dependent  on  automobiles. 
Economic  considerations  make  it  necessary  for  him  to  main- 
tain and  care  for  his  automobile  as  easily  and  with  as  little 
expense  as  he  used  to  keep  his  horse  and  carriage. 

Automobiles  have  given  rise  to  extraordinary  develop- 
ments in  modern  industry  and  vast  changes  in  methods  of 
transportation  and  living.  Statistics  of  the  number  of 
registered  automobiles  give  some  idea  of  the  extent  and 
nature  of  their  use.  In  1900  there  were  less  than  20,000 
automobiles  in  the  United  States.  In  1910  there  were  about 
50,000.  In  1921  there  are  over  10,000,000.  At  the  present 
rate  of  production  about  2,000,000  automobiles  are  manu- 
factured annually  in  the  United  States,  a  large  part  of  these 
being  for  export  to  foreign  countries. 

With  this  enormous  growth,  the  problem  of  an  adequate 
supply  of  fuel  for  automobiles  has  become  increasingly 
difficult.  At  present  gasoline  is  used  more  extensively  than 
any  other  substance,  but  at  times  during  recent  years  the 
demand  has  exceeded  the  supply.  Heretofore  a  balance 
between  supply  and  demand  has  been  partially  brought 
about  by  (1)  decreasing  the  demand  by  designing  the  auto- 
mobile parts  that  have  to  do  with  combustion  so  that  heavier 


2  GASOLINE  AUTOMOBILES 

and  cheaper  grades  of  gasoline  may  be  used,  (2)  reducing  the 
weight  of  automobiles  so  that  the  engine  has  less  load  to  carry, 
and  (3)  increasing  the  supply  by  the  use  of  new  methods 
of  distillation  and  the  development  of  new  oil  fields.  The 
present  high  price  of  gasoline  together  with  the  increased 
cost  of  labor  for  automobile  repairs,  has  spurred  the  owners 
to  cut  down  the  cost  by  taking  more  intelligent  interest  in 
economical  operation  and  proper  care  of  their  automobiles, 
with  the  object  of 

(1)  Eliminating  the  inconvenience  of  poorly  operating 

machines. 

(2)  Keducing  the  charges  for  repairs  and  replacement 

of  broken  and  worn  parts. 

If  the  efforts  to  decrease  demand  and  increase  supply 
still  refuse  to  yield  an  adequate  supply  at  a  corresponding 
price  reduction,  other  fuels  doubtless  will  become  important 
rivals  of  gasoline.  In  fact,  a  further  increase  of  less  than 
fifty  per  cent  in  the  price  of  gasoline  will  make  alcohol  an 
important  competitive  fuel. 

Classification  of  Automobiles.  The  various  kinds  of  auto- 
mobiles may  be  classified  according  to  (1)  kind  of  motive 
power;  (2)  kind  of  service.  These  may  be  tabulated  as 
follows : 

1.  Kind  of  Motive  Power: 

a.  Steam  Engine 

b.  Electric  Motor 

c.  Gasoline  or  Alcohol  Engine. 

2.  Kind  of  Service: 

a.  Pleasure  automobiles. 

b.  Commercial  automobiles   (trucks). 

The  following  chapters  will  be  devoted  to  the  consideration 
mainly  of  pleasure  automobiles  that  receive  their  power 
from  gasoline  engines  though  in  the  next  few  paragraphs 
the  advantages  and  disadvantages  of  steam  automobiles  and 
electric  automobiles  will  be  explained. 

Steam  Automobiles.  A  steam  driven  automobile  has  im- 
portant points  of  difference  when  compared  with  a  gasoline 


AUTOMOBILE  TYPES  AND  PARTS  3 

automobile,  the  chief  one  being  that  the  modern  steam 
automobile  has,  besides  an  engine,  a  steam  boiler  completely 
equipped  with  pumps,  water  and  steam  gages,  safety  valve, 
condenser,  etc.  Thus  it  is  a  complicated  apparatus,  requir- 
ing careful  attention.  The  steam  automobile  as  compared 
with  the  gasoline  and  electric  kinds  has  several  disadvan- 
tages, the  most  important  among  them  being  that  it  cannot 
be  made  instantly  available  for  service.  Even  with  the 
most  modern  types  of  quick-firing  portable  steam  boilers 
it  takes  several  minutes  to  heat  water  sufficiently  to  generate 
enough  steam  to  start  the  engine.  Other  disadvantages  are 

(1)  that  large  quantities  of  water  are  needed  for  making 
steam  so  that  a  considerable  weight  of  water  must  be  carried ; 

(2)  that  if  there  is  no  provision  for  condensing  the  steam  and 
using  the  water  over  again  in  the  boiler,  the  distance  that 
can  be  traveled  between  refillings  is  very  limited;  (3)  that 
the  cloud  of  steam  discharged  from  such  an  engine  especially 
in  cold  weather  is  annoying  to  the  -drivers  of  other  con- 
veyances;   (4)    that  both  the   open  flame  which  furnishes 
heat  to  the  boiler  and  the  high  steam  pressure  which  is 
necessary  are  objectionable  because  of  the  danger  of  fire 
and  destructive  explosions. 

There  are,  however,  advantages  in  steam-driven  vehicles, 
of  which  the  most  obvious  is  the  simplicity  of  speed  control. 
Merely  by  adjusting  an  ordinary  throttling  valve  the  pres- 
sure of  the  steam  admitted  to  the  engine  can  be  closely 
regulated  and  thereby  also  the  speed  of  the  automobile. 
The  shifting  of  gears  is  never  necessary  on  hilly  roads  or 
in  starting  or  reversing  since  a  simple  movement  of  links 
controlling  the  steam  valves  gives  all  necessary  control  of 
speed,  power,  and  forward  and  backward  movement. 

Electric  Automobiles.  For  simplicity  and  easy  control 
electric  automobiles  approach  the  ideal.  By  merely  moving 
a  small  lever-switch,  all  the  operations  of  changing  speed, 
reversing  and  maximum  power  are  positively  controlled.  An 
electric  automobile  involves,  however,  the  inconveniences 
of  carrying  a  very  heavy  electric  battery  made  mostly  of 


4  GASOLINE  AUTOMOBILES 

lead  in  order  to  furnish  the  power  necessary  for  a  high 
speed  and  travelling  in  hilly  country,  and  of  having  the  bat- 
tery recharged  at  a  properly  equipped  place,  every  hundred 
miles  or  less. 

Gasoline  Automobiles.  Gasoline  automobiles  are  the  real 
subject  of  these  chapters,  and  all  the  following  pages  will 
be  devoted  to  the  detailed  descriptions  of  their  parts.  In 
construction  and  methods  of  operation,  when  compared  with 
the  steam  and  electric  kinds,  gasoline  automobiles  have  the 
disadvantage  of  having  a  type  of  engine  which  cannot  be 
started  without  special  and  expensive  auxiliary  equipment. 
Furthermore,  this  type  of  engine  in  order  to  avoid  "stalling" 
if  overloaded  at  normal  engine  speed,  requires  a  system  of 
speed-change  gearing  between  the  engine  and  the  wheels 
on  the  driving  axle. 

Various  mechanical  and  electrical  devices  however  have 
been  applied  to  the  modern  gasoline  automobile,  so  that  in 
spite  of  the  disadvantages  named,  it  has  practically  a  non- 
competitive  field  for  general  touring,  pleasure,  and  business 
services.  The  great  advantage  in  its  favor  is  that  it  can 
carry  a  sufficient  supply  of  gasoline  for  fuel,  oil  for  lubrica- 
tion and  water  for  cooling  the  engine,  to  run  from  two 
hundred  to  four  hundred  miles  without  refilling.  As  the 
result  of  very  careful  and  thoughtful  designing,  it  can  be 
run  day  after  day  with  little  attention,  and,  if  carefully  and 
intelligently  operated,  with  only  small  charges  for  repairs 
and  replacement  of  parts. 

Types  of  Automobile  Bodies.  Automobiles  are  given 
various  names  according  to  the  style  or  type  of  the  body, 
which  is  generally  taken  to  mean  all  that  part  above  the 
wheels  to  the  rear  of  the  sheet  metal  hood  over  the  engine. 
The  touring-car  body  (Fig.  1)  is  the  one  most  generally  used 
on  pleasure  cars.  It  has  always  front  and  rear  seats  and  some- 
times additional  folding  seats,  and  is  made  with  a  folding 
top.  The  roadster  (Fig.  2)  resembles  a  touring  car  in  general 
lines  but  has  only  one  seat.  The  coupe  (Fig.  3)  has  only 
one  seat  and  is  made  with  an  enclosed  body  and  glass  windows. 


AUTOMOBILE  TYPES  AND  PARTS 


The  cabriolet  (Fig.  4)  is  a  semi-closed  roadster  with  folding 
top.  The  sedan  (Fig.  5)  has  an  entirely  enclosed  body,  and 
differs  from  the  coupe  in  having  more  than  one  seat.  The 
limousine  (Fig.  6)  has  a  driver's  seat  in  front,  which  is 
usually  open  at  the  sides  and  separated  by  a  partition  from 
the  passenger  seats  behind. 

The  touring-car,  roadster,  and  cabriolet  have  tops  which 
can  be  let  down  and  folded  at  the  rear;  but  as  a  rule  such 
automobiles  are  now  not  operated  as  much  as  formerly  with 


FIG.  1.— Touring  Car. 


FIG.  2.— Roadster. 


FIG.  3. — Coupe. 


FIG.  4.— Cabriolet. 


FIG.  5. — Sedan. 


FIG.  6. — Limousine. 


the  top   down   and   folded,   except   on  a   tour  in  unusually 

picturesque  country  where  a  standing  top  shuts  off  the  view. 

The  important  principles  of  present  body  design  are 

(1)  Giving  a  low  appearance  to  the  automobile  by  the 
use  of  low  wheels,  a  high  back  on  the  rear  seat  of  touring 
cars,  and  a  low  angle  steering  column,  and 

(2)  Accentuating  the  length  by  the  use  of  stream  lines, 
that  is,  body  lines  which  blend  continuously  from  the  hood  to 
the  rear  seat. 


6  GASOLINE  AUTOMOBILES 

Eecent  automobile  designers  favor  a  low-hung  body,  most 
of  the  latest  models  having  the  floor  of  the  body  from  three 
to  five  inches  nearer  the  ground  than  in  the  automobiles 
made  several  years  ago.  The  automobile  with  the  low  body 
and  low  top  has  a  pleasing  appearance,  but  it  is  not  so 
easy  riding  as  the  high-hung  body  type,  and  is  not  so  con- 
veniently arranged  for  getting  in  and  out. 

The  latest  body  designs  are  intended  to  give  soft, 
straight-line  effects  without  necessarily  sacrificing  the  beau- 
tiful results  obtained  by  the  use  of  moderately  rounded 
corners.  With  too  many  curves  there  seems  to  be  no  char- 
acter to  the  body,  while  with  too  many  straight  lines  there 
is  harshness.  A  suitable  combination  of  the  two  is  required 
to  make  a  pleasing  design.  The  present  tendency  is  for 
the  roofs  of  enclosed  bodies  to  be  straight  and  nearly  flat 
with  straight  lines  for  the  doors,  because  distinctly  rounded 
corners  at  the  window  openings  and  at  the  doors  give  the 
impression  of  greater  weight  than  straight-line  corners,  and 
lightness  in  appearance  is  an  important  matter  in  present 
body  designs. 

The  weight  of  the  body  is  a  principal  factor  in  determin- 
ing the  necessary  strength  in  the  automobile  frame  and 
the  engine  power,  and  since  an  automobile  for  everyday 
use  does  not  usually  require  room  enough  for  seven,  and 
since  a  shortage  of  the  gasoline  supply  is  quite  possible, 
designers  of  automobiles  are  now  giving  more  and  more 
attention  to  the  requirement  of  lightness. 

Many  hoods  on  automobiles  have  more  louvres — as  the 
vertical  slots  in  the  side  of  the  hood  are  called — than  are 
necessary.  There  are  cases  where  the  ventilating  fan  fo.r 
cooling  the  engine  draws  nearly  as  much  air  through  the 
front  louvres  as  it  discharges  through  the  rear  ones.  For 
proper  and  efficient  operation,  the  cooling  air  should  enter 
only  from  the  front  of  the  automobile  and  only  the  dis- 
charged heated  air  pass  through  the  louvres  of  the  hood. 
Air  circulation  through  the  hood  can  be  easily  tested  by 
placing  a  piece  of  tissue  paper  so  as  to  cover  some  of  the 


AUTOMOBILE  TYPES  AND  PARTS  7 

front  louvres  and  observing  whether  the  draft  is  outward, 
as  it  should  be. 

For  winter  service,  demountable  tops  for  making  enclosed 
bodies  on  touring  cars  and  roadsters  are  being  sold  with 
the  object  of  making  them  all-year  automobiles,  but  because 
of  the  difficulty  of  making  the  tops  with  pleasing  body  lines 
and  neat  fittings,  there  is  not  much  demand  for  them;  the 
coupe,  sedan,  and  limousine  still  being  the  favorites  for  all- 
year  service. 

The  sedan  has  been  coming  into  more  general  use  of 
late  and  has  to  a  certain  extent  replaced  the  limousine. 
It  gained  favor  during  the  war  when  chauffeurs  went  into 
army  and  navy  service  in  large  numbers,  and  driving  had 
to  be  done  by  the  owner  or  by  a  member  of  his  family.  The 
sedan  made  it  possible  for  all  members  of  the  family  to 
sit  together,  without  one  of  their  number  being  shut  off 
by  a  glass  partition,  as  would  be  the  case  in  a  limousine, 
and  gave  protection  to  the  driver  in  stormy  weather.  The 
driver  of  a  sedan,  it  is  true,  is  at  a  disadvantage  as  compared 
with  the  driver  of  a  limousine,  because  he  cannot  hear  or 
see  so  readily  as  when  sitting  in  the  open;  but  except  for 
this  disadvantage,  the  sedan  is  almost  ideal  as  an  all-year 
transportation  automobile.  It  gives  satisfactory  ventilation 
and  a  fairly  unobstructed  view  for  the  passengers  in  prac- 
tically all  conditions  of  winter  and  summer  service  even 
when  touring,  and  certainly  for  winter  service  it  is  at  least 
far  more  satisfactory  and  comfortable  than  the  touring  car 
with  its  top  up  and  its  dilapitated  side  curtains. 

A  coupe  with  a  roomy  body  is  well  adapted  for  summer 
and  winter  touring  because  suit-cases,  traveling  bags,  and 
boxes  may  be  left  in  it  with  safety  in  a  public  garage  since 
the  windows  and  doors  of  the  car  can  be  locked. 

Flow  of  Power.  Before  explaining  the  details  of  auto- 
mobile construction  and  operation  it  will  be  helpful  to  trace 
the  flow  of  power  from  its  source  in  the  engine  to  the  rear 
wheels  which  drive  the  car. 

Power    in    a    gasoline    engine    originates    in    successive 


8  GASOLINE  AUTOMOBILES 

explosions  in  a  series  of  cylinders.  The  force  of  each  explo- 
sion is  communicated  through  a  set  of  pistons  moving  up 
and  down  in  the  cylinders  to  a  crankshaft  which  is  con- 
nected to  a  flywheel.  The  momentum  of  the  flywheel  makes 
the  flow  of  power  steady  and  smooth.  A  shaft  extending 
to  the  rear  from  the  center  of  the  flywheel  transmits  the 
power  through  the  friction  clutch  and  speed-change  gears 
to  the  axle  drive  shaft.  At  its  rear  end  the  central  drive 
shaft  engages  a  set  of  gears  called  the  differential.  The 
differential  gears  are  connected  to  two  rear  axle  shafts 


Emergency  Brake  Lever 


Speeckhange  Shifting  U 
'V 


Gasoline  Engint 
WfndShield      /Cylinder 


RearSpriny  ,• 


\    UniversalJoint  \ 
Axle  Dri've  Shaft 


'•  Differential  and 
Rear  Axle 


I  flynhettahd 
\  Friction  Ctufch 
Speed^hancje  dears 
or  Transmission 


Starting 
Crank 


FIG.  7.— Side  View   (Section)  of  Automobile. 

which  extend  to  right  and  left  and  in  turning  communicate 
the  power  to  the  rear  wheels  at  their  hubs. 

Parts  of  Gasoline  Automobiles.  The  engine  with  its 
radiator,  the  automobile  frame,  wheels,  steering  gear,  axles, 
springs,  friction  clutch,  speed-change  gears,  and  body*  are 
the  essential  parts  of  a  modern  gasoline  automobile.  These 
and  some  other  parts  of  minor  importance  are  shown  and 
labelled  in  Figs.  7  and  8,  the  first  of  these  shows  the  side 


*  All  the  parts  of  a  gasoline  automobile,  excluding  the  body  and 
hood  are  called  the  chassis  (from  a  French  word  meaning  to  chase  or 
run).  Some  automobile  engineers  also  exclude  the  engine  from  the 
chassis.  The  chassis  corresponds  to  the  running  gear  of  a  wagon. 


AUTOMOBILE  TYPES  AND  PARTS 


9 


view  of  an  automobile  with  a  touring  car  body  as  if  cut 
through  the  middle,  and  the  second  shows  the  same  auto- 
mobile (without  body  and  hood)  as  seen  when  looking  down 
from  the  top.  These  figures  give  a  good  idea  of  the  position 
and  relation  of  the  essential  parts. 

The  radiator  shown  at  the  front  of  the  automobile  in 
Fig.  7  is  really  an  essential  part  of  the  engine  (sometimes 
called  the  motor),  which,  by  burning  or  "exploding"  gasoline 
in  its  enclosed  cylinders,  like  C  in  the  figure,  turns  the  crank- 
shaft or  drive  shaft.  This  shaft  is  connected  at  the  front 
end  of  the  automobile  to  the  starting  crank  for  use  when  an 
engine  is  started  by  hand,  and  at  the  other  end  is  connected 
to  the  friction  clutch,  which  has  a  central  shaft  entering  the 


FIG.  8. — Top  View  of  Automobile  Chassis. 

speed-change  gear  box.  Strong,  interlocking,  or  meshing, 
gear  wheels  in  this  gear  box  are  on  short  shafts  which  can 
be  connected  up  in  several  ways  through  a  universal  joint 
to  the  axle  drive  shaft  connected  to  another  set  of  gears 
(called  the  differential)  in  the  enlarged  middle  portion  of 
the  rear  axle.  The  gears  in  the  rear  axle  are  rigidly  attached 
on  each  side  to  enclosed  rods  which,  when  rotated,  drive  the 
rear  wheels.  Power  from  the  engine  is  thus  transmitted  to 
the  rear  wheels,  which  by  their  gripping  on  the  ground  move 
the  automobile  forward  or  backward  as  desired.  The  engine, 
friction  clutch,  and  speed-change  gear  box  are  supported  on 
the  automobile  frame,  which  is  itself  supported  flexibly  on 
the  front  and  rear  axles  by  means  of  springs. 


10  GASOLINE  AUTOMOBILES 

Brakes  (Fig.  8)  for  stopping  the  automobile  usually  have 
inside  and  outside  bands  with  a  mechanism  to  tighten  them 
against  a  drum  on  each  rear  wheel  in  order  to  provide  the 
necessary  friction.  Steel  rods  and  links  connect  these  bands 
to  the  brake  pedal  and  to  the  emergency  brake  lever  in  front 
of  the  driver's  seat. 

The  muffler  is  in  nearly  all  automobiles  a  drum  or  cylinder 
into  which  the  exhaust  pipe  carries  the  exhaust  gases.  It 
is  used  to  stifle  the  noise  of  rapid  explosions,  which  would 
otherwise  be  deafening. 

The  purpose  of  the  tires  is  to  absorb  road  shocks  and 
make  riding  easy,  as  well  as  to  keep  the  automobile  from  jolt- 
ing to  pieces. 

Differential  Gears.  A  means  must  be  provided  in  auto- 
mobiles to  make  it  possible  to  drive  the  rear  wheels  so  that 
one  wheel  can  turn  faster  than  the  other  in  going  around 
a  corner.  The  rear  axle  is  made,  therefore,  in  two  separate 
pieces  or  separate  axles,  and  each  piece  is  connected  at  the 
middle  of  the  rear  axle  to  differential  gears.  This  gearing 
device  permits  the  two  rear  wheels  to  turn  at  different  speeds 
as  necessary  in  driving  along  a  curved  road  or  in  making  a 
sharp  turn.  If  differential  gears  were  not  provided  and  the 
two  rear  wheels  had  to  move  at  the  same  speed,  when  going 
around  a  curve  the  wheel  on  the  inside  would  have  to  slip 
on  the  road  bed  without  much  turning  motion.  It  would  be 
possible  to  get  around  a  curve  with  an  automobile  with  such 
a  single-piece  axle,  if  it  were  not  going  fast,  but  one  can 
easily  see  that  an  automobile  made  with  a  one-piece  axle 
would  be  difficult  to  steer  on  a  rough  road  and  would  soon 
wear  out  its  rear  tires  and  wheel  rims.  When  the  rear  end 
of  an  automobile  is  jacked  up  and  both  hind  wheels  are  off  the 
ground  if  the  engine  is  started  the  wheels  may  be  seen  to  turn 
at  different  rates  of  speed.  One  wheel  may  not  even  turn 
at  all.  This  behavior  is  perfectly  normal  and  is  due  to  the 
nature  of  the  differential. 

When  an  automobile  is  started  with  one  rear  wheel  on 
firm  ground  and  the  other  on  ice  or  thin  mud,  the  wheel 


AUTOMOBILE  TYPES  AND  PARTS  11 

on  slippery  ground  will  often  spin  while  the  other  does  not 
move  at  all.  This  is  only  another  illustration  of  the  peculiar 
working  of  the  differential  gears  and  divided  axle  shaft. 

The  special  tendency  of  automobile  wheels  to  spin,  slip, 
and  skid  is  offset  to  a  considerable  extent  by  the  use  of  chains 
and  other  friction  devices  which  give  the  wheels  a  fairly 
firm  grip  on  slippery  ground.  A  common  type  of  rear  axle, 
divided  in  the  middle  and  turned  by  the  differential  gears 
is  shown  in  Fig.  9.  The  figure  shows  that,  though  the  rear 
axle  carries  the  power  for  moving  the  wheels  it  does  not  have 
to  bear  the  weight  of  the  body.  This  burden  is  borne  by 
the  heavy  casing  or  housing,  usually  made  of  steel,  in  which 
the  axle  shafts  and  differential  gearing  are  enclosed.  At  A 


Differential  Gears 


Axle  Casing  or  Housing 

FIG.  9. — Example  of  Bear  Axle. 

and  B  in  the  figure  there  are  plates  or  lugs  on  the  housing. 
To  these  are  attached  the  rear  springs  on  which  the  body 
frame  is  supported.  When  properly  made  and  put  together 
the  rear  axle  housing  is  sufficiently  tight  to  keep  out  road 
dust  and  to  keep  in  the  heavy  oils  which  are  used  for  the 
purpose  of  lubricating  the  moving  parts  and  deadening  their 
noise.  Sometimes  a  rear  axle  which  has  been  taken  apart 
and  reassembled,  sputters  oil  over  the  wheels,  brakes,  or 
other  parts.  When  this  is  the  case,  the  parts  have  not 
been  put  together  tightly.  Ordinarily  differential  gears 
cause  very  little  trouble  if  their  housing  is  kept  well  filled 
with  oil  of  good  lubricating  value  and  of  proper  thickness 
to  prevent  leakage. 

Friction  Clutch.     The  power  from  the  engine  is  trans- 
mitted from  the  flywheel  on  the  engine  crankshaft  to  the 


12  GASOLINE  AUTOMOBILES 

other  parts  of  the  automobile  power  plant  by  a  friction 
device  which  can  be  made  to  engage  or  disengage  with  the 
inside  surface  of  the  flywheel.  This  friction  device  is  called 
the  clutch.  (Marked  in  Figs.  7  and  8.)  By  the  use  of  the 
clutch  it  is  possible  to  start  or  stop  an  automobile  with  a 
gradual  change  of  speed.  Without  a  clutch,  starting  or  stop- 
ping would  be  jerky  and  uncomfortable  in  the  extreme.  A 
skillful  operator  will  let  his  clutch  in  so  slowly  and  gently 
when  starting  that  the  automobile  picks  up  speed  gradually 
and  smoothly. 

The  ability  to  make  a  good  stop  is  an  important  matter 
in  driving.  There  are  three  ways  to  stop  an  automobile: 
(1)  by  disengaging  the  clutch  and  letting  the  automobile 
glide  along  until  it  stops;  (2)  by  disengaging  the  clutch  and 
at  the  same  time  applying  the  foot  brake;  (3)  by  disengaging 
the  clutch  and  applying  the  foot  brake  and  also  the  hand 
emergency  brake.  At  critical  times  inexperienced  operators 
sometimes  forget  momentarily  how  to  stop  quickly.  Most 
automobiles,  except  the  Ford,  will  be  stopped  for  emergencies 
by  pushing  both  feet  forward  upon  the  clutch  and  foot-brake 
pedals  and  pulling  on  the  emergency  brake  lever.  If  all 
operators  were  well  drilled  in  these  movements  as  a  single 
operation  there  would  be  very  few  collision  accidents;  pro- 
vided, of  course,  the  brakes  are  kept  in  good  adjustment. 
The  method  of  stopping  by  running  into  a  stone  wall  or 
other  obstruction  need  only  be  mentioned,  although  in  case 
the  brakes  and  speed-change  gears  fail  to  control  the  auto- 
mobile when  it  is  going  down  a  steep  curved  mountain  road, 
there  may  be  occasion  to  use  it. 

Speed-change  Gears.  Provision  must  be  made  in  all 
automobiles  driven  by  gasoline  engines  for  a  system  of  gears 
or  a  similar  device  to  permit  both  changing  the  speed  of 
the  automobile  without  changing  that  of  the  engine,  and 
reversing  or  running  the  automobile  backward,  as  a  gasoline 
engine  itself  can  run  in  only  one  direction.  Changing  gears 
is  often  called  "shifting  gears."  Speed-change  gears  may 
be  set  in  such  a  position  as  to  be  entirely  disconnected  from 


AUTOMOBILE  TYPES  AND  PARTS  13 

the  axle  drive  shaft.  They  are  then  said  to  be  "in  neutral." 
The  gears  should  always  be  in  neutral  when  the  engine  is 
being  started,  or  when  "idling";  that  is,  running  while  the 
automobile  stands  still. 

The  reasons  for  "shifting"  gears  are  (1)  to  get  more 
pulling  force  on  hilly  and  rough  roads;  (2)  to  get  very  low 
automobile  speed  without  reducing  the  engine  speed  so  as 
to  risk  its  stopping  by  getting  "stalled";  (3)  to  "reverse" 
or  to  run  the  automobile  backward.  Speed-change  gears  are 
also  called  the  transmission. 

The  differential  gears,  the  friction  clutch,  and  the  speed- 
change  gears  have  been  referred  to  here  in  only  a  general 
way  so  as  to  give  an  idea  of  the  operation  of  the  various 
essential  parts  of  an  automobile.  In  later  chapters  these 
parts  will  be  described  with  detailed  explanations  and  illus- 
trations. 

Universal  Joints.  A  little  study  of  Fig.  7  will  show  that 
the  engine,  clutch,  and  speed-change  gears  are  rigidly  mounted 
on  the  frame  and  form  a  unit  with  it,  while  the  rear  axle 
and  rear  wheels  form  another  unit  which  rests  upon  the 
ground  and  supports  the  frame  by  means  of  the  springs.  The 
axle  drive  shaft,  which  connects  these  two  units,  must  be 
free  to  move  somewhat  in  any  direction,  to  be  adjustable 
when  the  car  swerves  slightly  or  when  the  rear  axle  moves 
up  and  down  as  the  wheels  pass  over  rough  places  in  the 
road.  The  axle  drive  shaft  is  therefore  provided  with  a  joint 
which  allows  flexible  rotary  motion  between  the  speed-change 
gears  and  the  rear  axle.  This  kind  of  joint  is  called  a 
universal  joint.  Fig.  10  shows  a  typical  universal  joint  for 
an  axle  drive  shaft. 

Steering  Gears.  The  steering  wheel  which  is  used  in 
guiding  the  automobile  is  connected  as  shown  in  Fig.  11 
by  rods,  levers,  and  gears  (all  called  the  steering  gear)  to 
the  ends  of  the  front  axle  near  each  of  the  front  wheels. 
Turning  the  steering  wheel  in  clockwise  direction  draws  in 
the  right-hand  front  wheel  toward  the  body  and  swings  out- 
ward the  left-hand  front  wheel  so  that  the  automobile  is 


14 


GASOLINE  AUTOMOBILES 


guided  to  move  toward  the  right-hand  side.  Anti-clockwise 
movement  of  the  steering  wheel  guides  in  the  opposite  direc- 
tion. Nearly  all  automobiles  now  made  in  America  use  the 
left-hand  drive,  that  is,  the  steering  wheel  is  on  the  left-hand 


FIG.  10. — Universal  Joint. 


side  of  the  automobile  so  that  the  driver  sits  on  the  left- 
hand  seat. 

The  front  axle  of  most  automobiles  is  made  of  a  solid 
steel  forging.     It  does  not  turn  on  a  "fifth  wheel"  as  on 


Steering  Wheel 


ffiah-f-  Yoke  and 

Knuckle  -,.       Automobile  Frame 


'  SfaerirrgLeverAnn 

*7  L,nk 
Front  Axle  /^  y^  gndKnuekle 

Fie.  11. — Example  of  Steering  Gear. 

a  wagon  or  carriage,  but  is  attached  by  means  of  flexible 
springs  to  the  body  frame  work.  The  wheels  are  on  short 
horizontal  spindles  which  are  movable  for  steering. 

Frame  and  Springs.     The  automobile  frame  is  a  frame- 


AUTOMOBILE  TYPES  AND  PARTS  15 

work  made  usually  of  steel  but  sometimes  of  wood,  to  support 
the  engine,  radiator,  friction  clutch,  speed-change  gear  box, 
engine  drive  shaft,  and  all  other  parts  not  attached  directly 
to  the  axles.  It  is  claimed  that  a  wooden  frame  transmits 
less  vibration  and  is  easier  riding  than  a  steel  frame,  but 
actually  there  is  little  difference  between  frames  of  steel  and 
of  wood  when  they  are  equally  well  designed.  The  frame  is 
supported  on  springs  as  shown  in  the  figures.  A  long  frame 


FIG.  12. — Spring  Leaves. 

makes  possible  a  long  wheel  base,  which  is  the  distance 
measured  between  the  centers  of  the  front  and  rear  axles. 
This  is  considered  desirable  since  an  automobile  with  a  long 
wheel  base  usually  rides  more  comfortably  than  one  with  a 
short  wheel  base. 

Automobile  springs  are  made  in  exactly  the  same  way  that 
springs  have  been  made  for  a  hundred  years  for  use  in  horse- 
drawn  carriages.  The  usual  kind  of  springs  used  for  attach- 


FIG.  13. — Spring  Leaves  Assembled. 

ing  the  automobile  frame  to  the  axles  is  made  oT~a  number 
of  flat  steel  plates  called  leaves  (Fig.  12),  which  are  tapered 
at  the  ends  and  bent  into  curved  shapes  as  shown  in  Fig.  13, 
each  leaf  being  given  a  little  greater  curvature  than  the  next 
longer  one.  The  leaves  for  a  complete  spring  are  pressed 
together  and  fastened  with  clamps.  In  addition  to  the  clamp- 
ing, the  leaves  are  sometimes  put  together  more  permanently 
with  a  bolt  passing  through  the  middle  of  each  leaf  (Fig.  14). 
Although  all  automobile  body  springs  are  made  by  the 


16 


GASOLINE  AUTOMOBILES 


same  general  method,  there  are  several  types  or  arrangements 
in  use. 

Full  Elliptic  Springs.  A  spring  made  by  fastening  to- 
gether with  hinged  ends  two  sets  of  leaves  as  shown  in  Fig.  15 
is  called  a  full  elliptic  spring.  It  gives  very  easy  riding 
and  in  this  respect  is  most  satisfactory,  but  it  is  not  generally 


FIG.  14. — Bolted  Automobile  Spring.  FlG.  15. — Full  Elliptic  Spring. 

used  for  automobiles  because  it  takes  up  too  much  room  to 
be  adaptable  to  low-hung  automobile  bodies.  It  is  attached 
to  an  automobile  by  fastening  the  middle  of  the  top  part  to 
the  automobile  frame  and  the  middle  of  the  lower  part  to 
the  axle. 


FIG.  16. — Three-quarters  Elliptic  Spring. 

Three-quarters  Elliptic  Spring.  Fig.  16  shows  a  kind  of 
automobile  spring  made  with  a  set  of  leaves  at  the  bottom 
which  are  hinged  to  half  of  a  similar  set  at  the  top.  This 
type  is  called  a  three-quarters  elliptic  spring.  It  is  attached 
to  the  automobile  frame  at  the  end  of  the  short  top  part  at 
A  while  the  free  end  of  the  longer  bottom  part  is  fastened 


AUTOMOBILE  TYPES  AND  PARTS  17 

to  a  pin  bolted  to  the  side  of  the  frame  at  B.  The  two  ends 
of  the  spring  are  joined  by  a  pin  at  C.  The  axle  is  fastened 
to  the  middle  of  the  lower  part. 

Semi-Elliptic  Springs.     Fig.  17  consists  simply  of  a  set 
of  spring  leaves  like  those  shown  in  Fig.  13  but  in  an  inverted 


FlG.  17. — Semi-Elliptic  Spring. 

position.  This  type  is  shown  as  commonly  attached  to  front 
axles.  It  is  usually  attached  by  fastening  one  end  with  a 
hinged  connection  by  means  of  a  pin  to  the  front  end  of 
the  automobile  frame  at  A,  the  middle  part  to  the  axle  as  at  B, 
and  the  other  end  is  hung  by  means  of  a  link  suspended  from 


TIG.  18. — Cantilever  Spring. 

a  pin  attached  to-  the  side  of  the  automobile  frame.  When 
used  as  a  rear  spring  the  method  of  attachment  is  essentially 
the  same. 

Cantilever  Spring.    Fig.  18  illustrates  a  cantilever  spring 
which  is  a  single  set  of  spring  leaves  flexibly  attached  to  the 


18 


GASOLINE  AUTOMOBILES 


side  of  the  automobile  frame  at  one  end  and  at  the  middle, 
while  the  other  end  is  rigidly  fastened  to  the  rear  axle.  As 
shown  in  the  figure  the  spring  is  clamped  securely  at  the 


FIG.  19.— Platform  Springs. 

middle  to  a  block  B,  which  is  itself  supported  and  turns  on 
a  pin  P  bolted  to  the  side  of  the  frame. 

Platform  Spring.     Fig.  19  consists  of  two  semi-elliptic 
springs  each  attached  at  one  end  by  links  to  the  side  of  the 


FlO.  20.— Inverted  Semi-Elliptic  Spring 
(Ford  Type  Front  Spring). 

frame,  at  the  middle  to  the  rear  axle,  and  at  the  other  ends 
by  means  of  links  to  a  third  spring,  fastened  at  the  middle 
to  an  extension  of  the  frame. 

Inverted  Semi-Elliptic  Springs.    Figs.  20  and  21  are  used 


FIG.    21.— Inverted    Semi-Elliptic    Spring 
(Ford  Type  Bear  Spring). 

on  some  light  weight  automobiles  because  of  simplicity 
and  cheapness  in  construction.  Only  one  spring  is  used 
at  the  front  (Fig.  20)  and  only  one  at  the  rear  (Fig.  21). 


AUTOMOBILE  TYPES  AND  PARTS  19 

In  each  case  the  spring  is  attached  at  the  middle  to  the 
frame  with  its  length  parallel  to  the  axle,  and  the  two  ends 
are  fastened  by  links  to  the  axle  near  the  wheels. 

Lubrication  of  Springs.  The  first  automobiles  were  built 
without  provision  for  reducing  the  friction  of  the  springs. 
Neither  the  bolts  used  nor  the  holes  in  the  springs  into  which 
they  fitted  were  carefully  made  to  give  smooth  working 
surfaces,  and  there  was  continuous  squeaking.  The  springs 
of  modern  automobiles,  however,  are  provided  at  all  pin 
connections  or  other  flexible  attachments  with  oil  or  grease 
cups  for  lubrication.  Some  types  of  springs  are  made  with 
small  depressions  which  are  filled  with  a  mixture  of  graphite 
and  lubricating  grease,  in  order  to  eliminate  friction  between 
the  leaves.  These  provisions  for  lubrication  together  with 
carefully  made  and  low-friction  linings  or  bushings  for  the 
bolt  holes  have  made  squeaking  at  the  spring  joints  easily 
avoidable. 

Automobile  Engines.  The  engine  of  a  gasoline  auto- 
mobile furnishes  the  driving  power.  It  is  usually  made 
with  a  number  of  cylinders  in  which  occurs  the  burning  or 
exploding  of  a  highly  combustible  mixture  of  gasoline  vapor 
and  air,  which  furnishes  the  power.  As  a  rule  the  larger 
the  number  of  cylinders  the  more  even  and  steady  the 
propelling  power  will  be.  The  "explosions"  in  a  one- 
cylinder  engine  for  instance,  are  strong,  few,  and  far  be- 
tween, making  this  kind  of  engine  unusually  noisy.  Two- 
cylinder  engines  are  not  much  used  on  automobiles,  and 
three-cylinder  engines  practically  never.  Four-cylinder 
engines  are  used  more  than  any  others,  since  with  this 
number  of  cylinders  it  is  possible  to  make  the  individual 
cylinders  so  small  that  none  of  the  " explosions"  will  be 
noisy  and  a  sufficiently  uniform  turning  movement  is  secured 
on  the  driving  shaft  to  give  easy  and  steady  running  quali- 
ties. In  a  four-cylinder  engine  there  is  a  power  impulse 
every  half  revolution,  in  a  six-cylinder  engine  every  one- 
third  revolution,  in  an  eight-cylinder  engine  every  one- 
quarter  revolution,  and  in  a  twelve-cylinder  engine  every 


20  GASOLINE  AUTOMOBILES 

one-sixth  revolution.  The  reasons  for  this  are  not  explained 
here  but  will  be  fully  discussed  in  the  next  chapter.  It 
should  be  clear,  however,  from  this  statement  that  with 
increased  number  of  cylinders  in  an  automobile  engine  there 
is  greater  so-called  "  flexibility "  with  smoother  running, 
easier  starting,  and  less  vibration.  Eight-cylinder  and 
twelve-cylinder  engines  because  of  the  uniformity  of  the 
"flow  of  power"  can  be  operated  at  very  slow  speed  with- 
out using  speed-change  gears,  except  for  starting  and  for 
exceptionally  heavy  pulling  and  are  able  to  "pick  up" 
speed  much  more  rapidly  than  the  automobile  having  a 
four-cylinder  engine. 


CHAPTER   II 
AUTOMOBILE   ENGINES 

The  detailed  study  of  gasoline  automobiles  begins 
naturally  with  the  most  important  part,  the  engine,  or  the 
"motor"  as  it  is  commonly  called  in  the  automobile  industry. 
In  the  following  pages,  however,  the  name  engine  will  be 
used  exclusively  to  avoid  confusion  in  later  chapters  when 
the  name  "motor"  will  be  used  in  referring  to  the  electric 
motor  of  starting  systems.  Good  understanding  of  the  prin- 


Intafa  Valve  I  Open, 
Valve  E  Closed 


^  WATER  JACKET 


FlG.  22. — Cylinder  of  Gasoline  Engine. 

ciples  of  operation  and  of  the  important  details  of  the 
automobile  engine  should  be  a  part  of  the  education  of 
every  automobile  operator  or  driver.  Knowing  how  to  cor- 
rect faulty  adjustments  in  the  engine  and  in  its  auxiliary 
equipment  as  soon  as  they  occur  is  the  best  insurance  against 
nerve-racking  annoyances  and  large  expenses  for  repairs. 
Gasoline  Engine  Operation.  The  power  of  a  gasoline 
engine  comes  from  the  explosion  of  a  mixture  of  gasoline 
vapor  and  air  in  a  confined  space,  usually  in  a  closed  cylinder. 
Fig.  22  shows  the  cylinder  of  a  simple  type  of  gasoline  engine. 
The  explosive  mixture  enters  through  the  opening  opposite 
21 


22  GASOLINE  AUTOMOBILES 

the  valve  disk  I.  If  after  taking  in  a  quantity  of  explosive 
mixture,  this  opening  is  closed  and  the  mixture  is  exploded, 
the  movable  plunger,  or  piston  P  of  the  engine  will  be  forced 
by  the  explosion  toward  the  right-hand  end  of  the  cylinder, 
just  as  a  ball  is  driven  from  the  free  end  of  a  cannon  by  the 
explosion  of  the  powder  behind  it  (Fig.  23).  An  explosion 
is  really  nothing  more  than  the  practically  instantaneous 
burning  of  a  highly  inflammable  material.  In  a  gasoline 
engine  the  explosion  results  from  the  very  rapid  burning  of 
gasoline  vapor  mixed  with  air.  Such  a  mixture  when  put 
into  an  engine  cylinder  must  have  proper  proportions.  It 
is  possible  to  use  so  much  gasoline  that  the  mixture  is  too 
"rich"  to  explode  effectively.  On  the  other  hand,  with  too 


FIG.  23. — Explosive  Force  in  a  Cannon. 

little  gasoline  in  the  mixture  the  explosion  is  too  weak.  Be- 
tween the  mixtures  that  are  too  "rich"  and  those  that  are 
too  weak,  or  "lean,"  there  is  a  wide  range  of  mixtures  which 
are  highly  explosive.  The  proper  explosive  mixture  of  gaso- 
line vapor  and  air  is  of  fundamental  importance.  In  the 
following  chapters  there  will  be  frequent  references  to  this 
subject. 

Fig.  24  represents  diagrammatically  a  gasoline  engine 
divided  through  the  center  in  cross-section,  showing  the 
cylinder  C  with  its  plunger,  or  piston.  On  the  left-hand 
side  is  the  intake  pipe  through  which  the  explosive  mixture 
enters  the  cylinder.  On  the  right-hand  side  is  the  exhaust 
pdpe  through  which  the  burned  mixture  called  exhaust  gases 
escapes  from  the  cylinder.  A  most  important  device  called 
a  carbureter  is  attached  to  the  end  of  the  intake  pipe.  This 


AUTOMOBILE  ENGINES  23 

device,  when  properly  adjusted,  mixes  automatically  the 
right  proportions  of  gasoline  and  air  for  the  explosive  mix- 
ture. The  parts  of  a  carbureter  are  delicate  and  can  be 
adjusted  so  that  the  proportions  of  the  mixture  may  be 
changed  to  suit  the  varying  conditions  of  engine  operations 
in  summer  and  winter,  in  high  and  low  altitudes. 

When  the  force  caused  by  the  explosion  of  the  mixture 
in  the  engine  cylinder  drives  the  piston  (Fig.  24)  downward 
this  motion  is  transmitted  through  the  connecting  rod  R 
to  give  rotary  motion  to  the  crank  shaft  8,  which  revolves 
and  on  each  explosion  stroke  receives  enough  force  to  move 
the  piston  up  and  down  during  the  return  stroke  as  well 
as  also  during  the  other  strokes  when  no  power  is  developed. 
A  heavy  wheel  on  the  crank  shaft,  called  a  flywheel,  is  used 
as  a  means  of  storing  up  energy  during  the  explosion  stroke 
to  be  used  later  in  turning  over  the  engine  during  the  other 
three  strokes  when  there  are  no  power  impulses.  From  the 
engine  crank  shaft  the  power  is  transmitted  by  means  to  be 
fully  described  later,  to  the  rear  wheels,  and  the  automobile 
thus  gets  its  driving  power.  The  steel  casing  which  surrounds 
the  crank  shaft  and  lower  part  of  the  connecting  rods  is  called 
the  crank  case. 

Engine  Types.  There  are  two  principal  kinds  of  gasoline 
engines,  named  according  to  the  number  of  up  and  down 
movements,  or  strokes  of  the  piston  occurring  between  one 
explosion  or  power  stroke  and  the  next  power  stroke.  The 
kind  used  almost  exclusively  for  automobiles  has  one  ex- 
plosion in  every  four  strokes  of  the  piston.  In  this  kind  of 
engine,  the  explosion  stroke  together  with  the  other  three 
strokes  (until  the  next  explosion)  are  called  its  cycle;  and 
because  there  are  four  strokes  in  its  cycle  it  is  called  a  four- 
stroke  or  four-cycle  engine.  Another  kind  of  engine  not 
often  used  on  automobiles  but  much  used  for  marine  purposes 
has  only  one  stroke  between  an  explosion  stroke  and  the 
next.  It  has,  therefore,  only  two  strokes  in  a  cycle  and  is 
called  a  two-stroke  or  two-cycle  engine.  In  every  piston 
engine  one  stroke  of  the  piston  occurs  every  half  revolution  or 


24 


GASOLINE  AUTOMOBILES 


half  turn  of  the  crank  shaft.  Briefly  then  a  standard  type 
of  automobile  engine  has  four  strokes  or  two  complete  revolu- 
tions of  the  crank  shaft  in  its  cycle. 


Intake  Pipe 


,Spark  PIug-K 


FIG.   24. — Automobile  Engine. 
Intake  Position. 


FIG.  25. — Automobile  Engine. 
Compression  Position. 


FIG.  26. — Explosion 
Position. 


FIG.  27. —  Exhaust 
Position. 


Four-stroke  Automobile  Engine.  Figs.  24,  25,  26,  27, 
show  the  positions  of  the  engine  piston  in  the  four  strokes 
in  a  four-stroke  cycle;  that  is,  from  the  beginning  say  of 
an  explosion  stroke  till  the  piston  is  back  again  in  position 


AUTOMOBILE  ENGINES  25 

for  the  next  explosion.  For  simplicity  of  explanation,  the 
description  of  what  takes  place  during  the  four  strokes  of 
such  a  cycle  will  begin  with  the  intake  or  suction  stroke,  as 
shown  in  Fig.  24  when  the  piston  is  moving  downward  in 
the  direction  of  the  arrow  to  draw  the  mixture  of  gasoline 
vapor  and  air  from  the  intake  pipe  into  the  cylinder.  During 
this  stroke  the  engine  must  suck  in  the  explosive  mixture 
just  as  an  air-pump  sucks  in  air  before  compressing  it,  or  as 
the  ordinary  wooden  pump  draws  water  by  suction  from  a 
well.  After  the  explosive  mixture  of  gasoline  vapor  and  air 
is  in  the  cylinder  the  intake  valve  I  closes,  making  an  air 
tight  chamber.  After  this  the  piston  rises  as  shown  in  Fig. 
25  and  compresses  the  imprisoned  mixture.  This  compression 
of  the  explosive  mixture  is  an  important  part  of  the  cycle, 
as  it  causes  an  explosion  pressure  from  three  to  five  times 
greater  than  would  be  possible  without  compression.  Com- 
pression also  serves  to  mix  more  evenly  the  gasoline  vapor 
with  the  air  and  at  the  same  time  raises  the  temperature  so 
that  good  ignition  is  made  easier.  Anyone  who  has  operated 
an  automobile  engine  in  both  winter  and  summer  knows  how 
much  more  easily  good  ignition  is  secured  with  warm  air  than 
with  cold  air. 

Just  at  the  beginning  of  the  next  downward  stroke  (Fig. 
26)  the  explosive  mixture  is  ignited  by  an  electric  spark  from 
a  device,  called  a  spark  plug  K,  located  in  the  top  of  the 
engine  cylinder.  The  combustion  resulting  from  this  ignition 
raises,  almost  instantly,  the  pressure  due  to  the  compression 
stroke,  which  is  from  50  to  75  pounds  per  square  inch  to 
about  300  pounds  per  square  inch.  On  this  explosion  stroke 
the  piston  is  driven  downward  with  great  force — between 
2000  and  3000  pounds  in  each  cylinder  according  to  the 
surface  of  the  piston,  and  by  means  of  the  connecting  rod 
this  force  is  transmitted  to  the  crank  shaft  of  the  engine. 

In  order  to  make  the  explosions  in  an  engine  cylinder 
as  strong  as  possible,  the  ignition  of  the  explosive  mixture 
should  occur  a  trifle  before  the  point  of  greatest  compression. 
Ignition  should  take  place,  therefore,  just  before  the  end  of 


26  GASOLINE  AUTOMOBILES 

the  compression  stroke.  The  faster  the  engine  is  running 
the  earlier  in  this  stroke  the  ignition  should  occur.  This  is 
what  is  meant  when  one  says  the  "spark"  or  ignition  should 
be  "advanced,"  that  is,  occur  earlier  at  high  than  at  low 
speed. 

Valve  Operation.  For  controlling  the  order  of  the  strokes 
of  a  gasoline  engine  there  are  usually  two  valves  for  each 
cylinder.  One  controls  the  suction  or  admission  of  the  mix- 
ture of  gasoline  vapor  and  air  into  the  cylinder  and  is  called 
the  intake  valve  marked  /  in  the  preceding  figures  (Figs. 
24-27).  Another  controls  the  discharge  of  the  burned  or 
exhaust  gases  and  is  called  the  exhaust  valve  E.  The  valves 
of  gasoline  automobile  engines  are  opened  and  closed  by 
mechanical  means  similar  to  that  shown  in  Fig.  24.  Both 
intake  and  exhaust  valves  have  vertical  rods  attached  cen- 
trally to  the  valve  disks  which  extend  downward  toward  the 
crank  case  on  each  side  of  the  cylinder.  These  rods  are 
called  valve  stems.  The  one  on  the  intake  valve  is  marked 
IS  (for  intake  Valve  /Stem)  and  the  one  on  the  exhaust 
valve  E8  (for  Exhaust  Valve  /Stem).  The  valve  disks  are 
normally  held  in  the  closed  position  by  the  force  of  strong 
spiral  springs  (not  shown  in  the  figures).  The  intake  valve 
/  is  opened  by  being  pushed  upward  by  the  "tooth"  T  on 
the  cam  shaft  at  the  left-hand  side  of  the  engine.  When 
the  engine  is  in  motion  this  cam  shaft  revolves  constantly  at 
half  the  engine  speed,  and  opens  the  valve  when  the  "tooth" 
T  is  pointed  vertically  upward.  If  this  fact  about  cam  shaft 
speed  is  kept  in  mind  it  will  be  easy  to  understand  the  valve 
operation  of  any  four-stroke  automobile  engine.  Every  time 
the  "tooth"  T  on  the  left-hand  cam  shaft  comes  around  in 
a  revolution  it  raises  upward  the  intake  valve  stem  IS  and 
valve  /  against  the  force  of  a  spring  which  tends  to  hold  it 
down. 

There  is  also  another  cam  shaft  on  the  right-hand  side  of 
this  engine  which  moves  the  exhaust  valve.  This  cam  shaft 
has  also  a  "tooth"  for  opening  the  valve  but  its  position 
is  different  from  that  of  the  "tooth"  T  during  each  of  the 


AUTOMOBILE  ENGINES  27 

engine  strokes  just  described.  The  exhaust  valve  is  kept 
tightly  closed  during  the  intake  stroke.  During  the  com- 
pression (Fig.  25)  both  valves  remain  closed  during  the  whole 
stroke  so  that  the  explosive  mixture  is  " trapped"  within 
the  cylinder  and  none  of  it  can  escape.  Both  valves  are 
closed  also  during  the  explosion  or  power  stroke. 

When  the  piston  is  at  the  bottom  of  the  explosion  stroke 
and  is  about  to  begin  the  next  upward  stroke,  called  the 
exhaust  stroke,  the  "tooth"  on  the  right-hand  cam  shaft  comes 
into  contact  with  the  valve  stem  E8  and  pushes  open  the 
exhaust  valve  E.  On  this  stroke,  as  the  piston  goes  up,  the 
space  in  the  cylinder  above  the  piston  becomes  continually 
smaller,  and  with  the  exhaust  valve  open,  the  burned  mixture 
is  driven  out  through  the  exhaust  pipe  into  the  atmosphere, 
clearing  the  cylinder  to  receive  the  next  fresh  explosive 
mixture. 

Summary  of  Four-stroke  Engine  Operation.  By  drawing 
down  the  engine  piston  during  the  suction  stroke  a  vacuum 
is  created  in  the  upper  part  of  the  cylinder.  At  the  right 
moment  the  intake  valve  is  opened  and  a  mixture  of  gasoline 
vapor  and  air  is  sucked  in.  Then  the  intake  valve  closes  and 
the  rising  piston  compresses  this  charge.  When  the  piston 
reaches  its  highest  point  an  electric  spark  is  introduced  through 
the  spark  plug.  The  explosion  stroke  gives  enough  power  to 
carry  the  crank  over  the  strokes  which  have  no  power 
impulses. 

There  are  four  strokes,  or  up  and  down  movements,  of 
the  piston  in  each  cycle  of  a  four-stroke  engine.  The  first 
which  draws  in  the  mixture  is  called  the  suction  stroke;  the 
next  is  the  compression  stroke,  the  third  is  the  explosion  or 
power  stroke,  and  the  fourth  is  the  exhaust  stroke,  when  the 
burned  gases  are  expelled  from  the  engine  cylinder.  During 
these  four  strokes  there  are  two  complete  revolutions  of  the 
crank  shaft.  The  explosion  or  power  stroke  does  all  the  useful 
work  in  turning  the  engine  crank  shaft,  which  moves  the 
automobile.  The  suction  and  the  compression  strokes  serve 
only  to  take  in  the  explosive  mixture  and  get  it  ready  for 


28  GASOLINE  AUTOMOBILE^ 

efficient  explosive  burning.  The  exhaust  stroke  serves  only 
for  cleaning  out  the  cylinder. 

Engine  Flywheels.  For  every  four  strokes  of  a  four- 
stroke  engine  there  are  three  "idle"  strokes  during  which 
no  power  is  developed.  During  these  "idle"  strokes  the 
pistpn  must  be  driven  from  the  crank  shaft,  and  in  most 
engines  the  power  to  keep  the  crank  shaft  moving  during 
these  "idle"  strokes  must  come  from  "stored  energy"  or 
momentum  in  a  flywheel.  Flywheels  as  provided  on  auto- 
mobile engines  are  usually  a  part  of  the  friction  clutch.  (See 
Chapter  1,  page  9.)  A  flywheel  is  made  extra  heavy  because 
it  is  difficult  to  stop  a  heavy  wheel  when  revolving  at  high 
speed.  A  flywheel  of  proper  weight  when  once  started  will 
keep  an  engine  running  for  some  time.  A  well  designed 
automobile  engine  of  six  or  more  cylinders  once  started  will, 
however,  keep  itself  going  without  a  flywheel  if  all  its  cylinders 
are  operating. 

Valve  and  Cylinder  Arrangements.  The  typical  engine 
shown  in  Figs.  24,  25,  26,  27,  has  the  intake  valves  on  one 
side  of  the  engine  cylinder  and  the  exhaust  valves  on  the 
other  side.  This  is  called  a  T-head  cylinder  because  the  top 
of  the  cylinder  resembles  the  letter  T.  It  is  shown  diagram- 
matically  also  in  Fig.  28.  This  arrangement  is  used  on  many 
of  the  larger  makes  of  automobiles  as  it  allows  room  for 
valves  of  wide  diameter.  As  such  valves  have  to  be  lifted 
but  slightly  off  their  seats  to  admit  sufficient  mixture  and 
to  carry  off  exhaust  gas,  they  make  little  noise  in  operation. 

Most  automobile  engines,  however,  are  constructed  with  a 
more  compact  valve  arrangement  called  an  L-Jiead  cylinder 
in  which  both  the  intake  and  exhaust  valves  are  on  the  same 
side  of  the  cylinder  as  shown  in  Fig.  29.  It  is  a  well  known 
fact  that  the  larger  the  surface  of  the  cylinder,  including 
the  valve  spaces  in  which  the  explosive  mixture  is  ignited  and 
exploded,  the  greater  will  be  the  losses  due  to  wasted  heat 
by  cooling.  On  this  account  an  engine  with  an  L-head  cylinder 
and  with  other  parts  the  same,  will  be  more  economical  in 
the  use  of  gasoline  than  one  with  a  T-head  cylinder. 


AUTOMOBILE  ENGINES 


29 


Fig.  30  shows  a  valve  and  cylinder  arrangement  called 
valve-in-the-head.  The  valves  are  in  the  center  of  the  top 
of  the  engine  cylinder  and  open  downward.  This  affords 
a  very  short  passage  for  the  explosive  mixture  into  the  cylinder, 
and  a  very  small  surface  around  the  valves  exposed  to  cooling. 
This  is  sometimes  called  an  I-head  cylinder.  "Valves-in-the- 
head"  have,  therefore,  special  advantages  as  regards  power 
and  economy,  but  they  are  likely  to  be  more  noisy  than  other 
types. 

Though  most  automobile  engines  are  at  present  made  with 
the  L-head  construction,  there  is  an  increasing  number  being 
built  with  the  ''valve-in-the-head"  arrangement. 


FIG.  28.— T-Head 
Engine   Cylinder. 


FIG.  29.— L-Head 
Engine   Cylinder. 


FIG.  30. — Valve-in-the- 

Head  Engine 

Cylinder. 


Slide  Valve  Engines.  The  elimination  of  noise  in  auto- 
mobile engines  has  always  been  an  important  consideration. 
It  is  well  known  that  a  great  deal  of  the  noise  in  engine 
operation  is  due  to  the  valves.  In  any  engine  in  which  the 
ordinary  so-called  poppet  valves  are  used  there  is  necessarily 
some  noise  from  the  valves,  especially  after  repairing,  if  the 
lengths  of  the  push  rods  are  not  carefully  adjusted.  On  the 
other  hand,  slide  valves  are  almost  noiseless  and  their  use 
on  all  kinds  of  engines  is  not  new.  In  fact,  the  first  gas 
engines  ever  built  were  made  with  slide  valves ;  but  on  account 
of  the  high  temperature  in  such  engines  there  was  excessive 
wear  and  warping  and  it  was  difficult  to  keep  the  exhaust 
valves  tight  enough  to  hold  the  compression  pressure. 


30 


GASOLINE  AUTOMOBILES 


Knight  Slide  Valves.  In  recent  years  a  type  of  engine 
has  been  developed  in  which  poppet  valves  are  successfully 
replaced  by  slide  valves.  These  slide  valves  have  a  relatively 
gradual  motion,  and  slide  over  the  intake  and  the  exhaust 
openings  in  the  cylinder,  instead  of  being  snapped  into  their 


Intake  Stroke 

Intake  Ports  Open 

Exhaust  Ports  Closed 


Compression  Stroke 
All  Ports  Closed  and  Sealed  by 
Ring  La  Cylinder 


Power  Stroke 

All  Ports  Closed  and 

Protected  by  Ring  in  Cylinder 


Exhaust  Stroke 
Intake  Ports  Closed 
Exhaust  Ports  Open 


FIG.   31. — Knight  Slide  Valves  and  Engine  Cylinder. 

seats  by  a  strong  spring,  as  is  the  case  with  poppet  valves. 
There  is,  however,  another  advantage  besides  the  elimination 
of  noise,  as  a  slide  valve  engine  develops  more  power  for  its 
size,  because  larger  intake  and  exhaust  valve  openings  can 
be  used.  Figs.  31  and  32  show  plainly  the  position  of  the 
piston  and  Knight  slide  valves  on  the  suction,  compression, 


AUTOMOBILE  ENGINES 


31 


explosion,  and  exhaust  strokes.     The  thickness  of  the  valves 
is  purposely  exaggerated  to  show  the  details  more  clearly. 

The  difference  between  the  operation  of  poppet  valves 
and  Knight  slide  valves  can  be  readily  understood  when  one 
considers  that  the  ordinary  poppet  valve  has  its  maximum 
opening  during  the  time  that  the  valve  stem  roller  rides  on 
the  point  of  the  cam.  This  roller  follows  accurately  the 


Exhaust  Valve 
Opening 


FIG.  32.  —  Details  of  Knight  Valves. 

irregular  surface  of  the  cam  only  at  low  and  moderate  speeds. 
At  high  speeds  the  cam  will  throw  the  valve  stem  instead 
of  lifting  it  so  that  the  action  cannot  be  the  same  at  high 
speeds  as  at  low.  On  the  other  hand,  in  a  Knight  slide  valve 
engine  the  intake  and  exhaust  passages  are  opened  and  closed 
at  exactly  the  proper  time,  and  these  passages  can  be  made 
large  enough  so  that  the  power  of  the  engine  is  increased  in 
proportion  to  the  increase  in  speed.  Another  advantage 
claimed  for  slide-valves  is  that  there  are  no  projecting  par- 


32  GASOLINE  AUTOMOBILES 

tides  of  metal  or  of  carbon  on  the  valves  to  remain  hot  after 
the  discharge  of  the  exhaust  gases  to  cause  premature  explo- 
sions of  the  incoming  fresh  mixture. 

Pistons  and  Piston  Rings.  Formerly  all  gasoline  engine 
pistons  were  made  of  gray  cast  iron.  Recently  a  number 
of  manufacturers  of  automobile  engines  have  been  using 
pistons  made  of  aluminum  alloys.  Aluminum  pistons  are 
much  lighter  than  those  made  of  cast  iron  and  therefore 
reduce  the  weight  to  be  supported  by  the  engine  crank  shaft. 
Reducing  the  weight  on  the  crank  shaft  reduces  also  the 
vibration  of  the  shaft  and  makes  an  engine  quieter  in 
operation.  Aluminum  is  a  better  conductor  of  heat  than  iron. 
The  use  of  this  metal  makes  it  easier  to  keep  the  pistons  cool. 

Engine  pistons  are  never  made  to  fit  tightly  in  the 
cylinders.  The  pistons  must  be  made  a  trifle  smaller  than  the 
inside  of  the  cylinders  to  make  provision  for: 

1.  A  film  of  oil  between  the  curved  part  of  the  piston 

and  the  walls  of  the  cylinder. 

2.  The   greater   expansion   of  the   piston   than   of   tha 

cylinder,   because  of   the  greater   heating   of   the 

piston. 

Aluminum  expands  more  than  cast  iron,  therefore  aluminum 
pistons  must  be  made  to  fit  more  loosely  in  the  cylinders  than 
those  of  cast  iron. 

It  is  not  economical  to  allow  the  explosive  mixture  to 
escape  between  the  pistons  and  the  cylinder  walls  into  the 
crank  case  during  the  compression  stroke.  To  prevent  such 
leakage,  the  pistons  are  fitted  with  elastic  cast-iron  rings, 
called  piston  rings,  placed  in  grooves  around  the  body  of 
each  piston.  As  a  rule,  three  rings  are  placed  in  each  piston 
as  shown  in  Fig.  33. 

The  most  satisfactory  piston  rings  are  of  the  concentric 
type  in  which  the  thickness  is  uniform  all  around  the  ring. 
The  varying  degree  of  elasticity  which  is  required  in  the 
ring  in  order  that  it  should  tend  to  expand  in  a  circle 
and  fill  the  cylinder  bore  is  attained  by  certain  peening 
methods.  The  butting  ends  of  the  ring  are  generally  finished 


AUTOMOBILE  ENGINES  33 

to  form  a  lapped  joint  at  forty-five  degrees.  There  has  been 
much  misrepresentation  in  the  matter  of  specially  designed 
piston-rings  which  attempt  to  form  a  more  perfect  seal  than 
is  afforded  by  the  lapped  joint.  The  fact  is  that  the  per- 
centage of  leakage  past  the  joint  is  such  a  small  part  or 
the  whole  that  any  improvement  in  this  regard  yields  result., 


FlG.  33. — Engine  Piston. 

too  small  to  measure.  On  the  other  hand,  the  simple  rugged- 
ness  of  the  plain  ring,  as  contrasted  with  the  complicated 
construction  associated  with  the  majority  of  special  piston- 
ring  designs,  has  everything  to  recommend  it  for  ordinary 
service. 

The  kind  of  piston  rings  most  used  are  shown  in  Figs. 


FIG.  34.— Typical  FIG.  35.— Peened 

Piston  King.  Piston  Eing. 

34  and  35.  Many  pistons  are  now  made  with  a  groove  below 
the  lower  piston  ring  shown  in  Fig.  33,  with  five  or  six 
holes  drilled  in  the  groove  through  the  piston.  The  piston 
ring  then  scrapes  the  oil  from  the  cylinder  wall  into  the 
groove  and  it  drains  back  into  the  crank  case  through  the 
holes  in  the  piston  walls.  This  is  intended  to  prevent  oil 
from  working  up  the  cylinder  walls  and  burning  in  the 


34  GASOLINE  A  UTOMOBILES 

combustion  chamber.  In  some  cases  another  groove  is  made 
near  the  bottom  of  the  piston  into  which  a  " wiper"  piston 
ring  is  fitted.  This  "wiper"  ring  is  used  to  prevent  oil 
from  getting  started  on  the  way  to  the  explosion  space 
in  the  cylinder. 

Piston  rings  are  subjected  to  considerable  wear.  When 
badly  worn,  the  rings  do  not  function  properly  and  let  oil 
pass  into  the  combustion  chamber.  The  oil  only  partially 
burns  during  the  explosions  and  leaves  a  black,  greasy 
deposit  on  the  spark  plugs  and  piston  heads.  This  deposit 
is  commonly  called  carbon  and  unless  removed  befouls  the 
engine  to  such  an  extent  as  to  lower  its  efficiency  very  per- 
ceptibly. Worn  piston  rings  also  permit  gasoline  to  work 
back  into  the  crank  case  and  mix  with  the  oil.  As  gasoline 
destroys  the  lubricating  quality  of  the  oil,  the  bearings  are 
subjected  to  undue  wear.  When  an  engine  smokes  badly 
and  consumes  unusual  quantities  of  oil  loose  piston  rings 
are  likely  to  be  the  cause.  Despite  the  fact  that  it  is 
economical  from  every  standpoint  to  keep  piston  rings  tight, 
a  great  many  automobiles  are  run  with  worn  rings. 

Crank  Shafts.  The  crank  shaft  of  an  automobile  engine 
must  be  made  very  strong;  because  it  must  support  the 
weight  of  the  pistons  and  connecting  rods  and  resist  stresses 
and  vibrations  produced  by  the  irregular  arrangement 
of  the  connecting  rods  on  the  shaft.  In  a  four-cylinder 
engine  there  are  usually  three  bearings  or  "rests"  for  the 
crank  shaft  as  shown  in  Fig.  36.  A  six-cylinder  engine  has 
usually  four  bearings  as  shown  in  Fig.  37,  although  some 
six-cylinder  engines  are  made  with  only  three  bearings.  On 
the  other  hand  some  four-cylinder  engines  have  five  bearings, 
that  is,  each  of  the  connecting  rods  is  between  two  bearings. 
There  is  a  similar  arrangement  for  some  six-cylinder  engines 
which  have  seven  bearings.  These  examples  are  given  to 
show  that  there  is  great  variation  in  the  number  of  bearings 
which  are  provided  for  the  engine  crank  shaft  in  different 
makes  of  engines.  Obviously  in  an  engine  with  a  larger 
number  of  bearings  there  will  be  less  vibration  of  the  crank 


AUTOMOBILE  ENGINES 


35 


shaft  than  in  an  engine  with  fewer  bearings.  On  the  other 
hand,  a  larger  number  of  bearings  add  materially  to  the 
expense  of  making  an  engine. 

Fig.  36,  illustrating  the  crank  shaft  of  a  four-cylinder 


Ftywheet 


FIG.  36. — Crank  Shaft  for  Four-Cylinder  Engine. 

engine  with  three  bearings,  shows  the  conventional  arrange- 
ment of  pistons  corresponding  to  the  firing  order,  No.  1, 
No.  2,  No.  4,  No.  3.  These  numbers  are  consecutive  on  the 
engine  for  the  cylinders  numbered  from  the  front  of  the 


Connecting  Rod  'Piston  Ring     ..--CrankShaft  Bearing 
Flywheel      /         \  ^Piston       /          ..••- Connecting  Rod  Bearing 


,.,-CrarT(  Shaft 

•'.. CranffShaff 

'  6ear 

.... Starting 

Nut 


FIG.  37. — Crank  Shaft  for  Six-Cylinder  Engine. 

automobile.  The  pistons  in  the  two  middle  cylinders  move 
up  and  down  together  and  the  pistons  in  the  two  end 
cylinders  similarly  move  together.  This  means  that  when 
the  No.  1  piston  is  on  the  compression  stroke,  No.  4  is  on 


36  GASOLINE  AUTOMOBILES 

the  exhaust  stroke  and  Xos.  2  and  3  are  respectively  on  the 
suction  and  explosion  strokes. 

Engine  Speeds.  The  maximum  speed  of  a  four-cylinder 
engine  is  about  eighteen  hundred  revolutions  of  the  crank 
shaft  per  minute.  The  highest  speed  of  six-cylinder  engines 
is  from  two  thousand  to  twenty-five  hundred  revolutions 
per  minute,  and  eight-  and  twelve-cylinder  engines  are 
usually  designed  for  a  maximum  speed  of  three  thousand 
to  thirty-five  hundred  revolutions  per  minute. 

Arrangement  of  Cylinders  in  Automobile  Engines.  Early 
automobile  engines  were  made  with  one  or  two  horizontal 
cylinders.  With  the  introduction  of  engines  with  four  ver- 
tical cylinders  came  an  era  of  great  improvement  in  auto- 
mobile construction.  This  kind  of  engine  is  compact, 
accessible,  and  can  be  built  in  units  giving  reasonably  high 
horsepower ;  also,  the  distribution  of  explosive  mixture  from 
a  single  carbureter  presents  no  difficulties.  The  useful  power 
range  of  a  four-cylinder  automobile  engine  may  be  con- 
sidered to  lie  between  four  hundred  and  eighteen  hundred 
revolutions  per  minute,  which  corresponds  to  an  automobile 
speed  of  from  twelve  to  sixty  miles  per  hour.  For  the  low 
speed  requirements  of  congested  automobile  traffic  the 
speed-change  gears  of  a  four-cylinder  engine  must  be  shifted 
frequently. 

The  next  improvement  in  automobile  engines  was  to 
increase  the  number  of  cylinders  from  four  to  six,  or  eight. 
These  engines  with  more  frequent  power  strokes  met  in- 
stantly the  demand  for  more  power,  more  flexibility,  more 
smoothness,  and  less  noisy  operation.  A  six-cylinder  auto- 
mobile engine  will  doubtless  be  a  standard  type  for  many 
years  as  it  has  many  advantages  over  a  four-cylinder  engine, 
and  avoids  much  of  the  complication  and  excessive  upkeep 
expense  of  eight-cylinder  and  twelve-cylinder  engines. 
There  are,  however,  certain  structural  difficulties  which  limit 
the  general  application  of  such  engines  in  cheaply  constructed 
automobiles.  The  crank  shaft  of  a  six-cylinder  engine  is 
relatively  long,  and  in  some  designs  weight  limitations  do  not 


AUTOMOBILE  ENGINES  37 

permit  making  it  as  stout  as  might  be  desired.  Because  of 
this  slenderness  there  is  a  certain  amount  of  twisting  which 
causes  considerable  vibration  of  the  crank  shaft  in  every 
revolution.  At  some  speeds  (called  "critical")  these  vibraT 
tions  become  excessive  and  disagreeable  to  passengers.  They 
are,  of  course,  more  noticeable  in  a  large  engine  of  high  power 
with  a  slender  crank  shaft  than  in  small  ones. 

The  next  step  in  the  development  of  automobile  engines 
was  the  introduction  of  eight-  and  twelve-cylinder  engines. 
Four-cylinder  engines  and  six-cylinder  engines  are  always 
made  with  the  cylinders  in  a  row.  Eight-cylinder  engines 
and  twelve-cylinder  engines  as  usually  made  should  be  con- 
sidered as  two  four-cylinder  engines  or  two  six-cylinder 
engines  built  up  with  the  same  crank  shaft  and  crank  case 
for  the  attachment  of  two  rows  of  cylinders.  It  is  easy 
to  see  that  to  some  extent  at  least,  an  eight-cylinder  engine 
must  have  the  disadvantages  of  a  four-cylinder  engine,  and 
that  a  twelve-cylinder  engine  will  correspondingly  have  the 
disadvantages  of  a  six-cylinder  engine. 

For  the  same  horsepower,  the  individual  cylinders  of 
an  eight-cylinder  engine  are  considerably  smaller  than  those 
of  a  four-cylinder  engine  of  the  same  horsepower,  and, 
because  the  moving  parts  of  individual  cylinders  are  lighter 
in  weight  there  is  less  vibration  than  in  a  four-cylinder 
engine.  The  objection  to  some  six-cylinder  engines  because  of 
vibration  of  a  slender  crank  shaft  applies,  of  course,  equally 
to  a  twelve-cylinder  engine,  except  that  the  method  of  con- 
struction with  two  rows  of  small  cylinders  permits  the  use 
of  a  crank  shaft  actually  shorter  than  would  be  installed 
in  a  six-cylinder  engine. 

The  best  authorities  agree  that  there  is  little  likelihood 
that  practical  automobile  engines  will  be  built  with  more 
than  twelve  cylinders. 

Compared  with  the  simplicity  of  construction  of  the 
standard  four-cylinder  and  six-cylinder  engines  there  are 
many  practical  difficulties  in  the  construction  of  an  auto- 
mobile engine  with  eight  cylinders  in  a  single  row.  Even 


38  GASOLINE  AUTOMOBILES 

a  six-cylinder  engine  has  the  disadvantage  of  having  a 
relatively  long  crank  shaft.  This  difficulty  is  obviously 
much  increased  with  eight  cylinders  in  a  row.  There  is 
also  the  further  disadvantage  that  with  eight  cylinders  in 
a  row  the  hood  of  the  automobile  is  excessively  long.  Eight- 
cylinder  engines  are,  therefore,  made  as  a  rule  in  two 
rows  of  four  cylinders  each,  with  the  cylinders  placed  in  most 
makes  so  that  each  row  is  at  an  angle  of  forty -five  degrees  from 
the  vertical  center  line  of  the  engine ;  in  other  words,  the 
two  rows  of  cylinders  are  made  with  an  angle  of  ninety 
degrees  between  them. 

The  advantages  of  eight  cylinders  over  four  other  than 
the  increased  power  are  as  follows : 

(1)  more  even  turning  power;  (2)  greater  flexibility; 
(3)  less  vibration.  Practically  continuous  power  is  obtained 
in  an  eight-cylinder  engine  because  one  of  its  cylinders 
gives  a  power  stroke  every  quarter  revolution  of  the  engine 
crank  shaft  and  each  one  of  these  power  impulses  lasts 
about  three-quarters  of  the  stroke,  which  is  the  same  as  saying 
that  the  power  impulse  is  effective  for  each  of  the  cylinders 
for  three-eighths  of  a  revolution.  It  is  obvious,  therefore, 
that  the  power  strokes  aided  by  the  momentum  of  the  fly- 
wheel, will  overlap  and  give  almost  perfectly  constant  power. 
This  explanation  should  make  it  clear  that  an  eight-cylinder 
engine  with  its  four  power  strokes  per  revolution  should 
give  more  uniform  power  than  a  six-cylinder  engine  with 
three  explosions  per  revolution,  and  that  it  will  be  twice  as 
smoothly  running  as  a  four-cylinder  engine  with  only  two 
explosions  per  revolution.  Fig.  38  shows  the  relative  con- 
tinuity or  "flow"  of  power  in  engines  having  one,  two,  four, 
six,  and  eight  cylinders. 

From  the  foregoing,  it  is  easy  to  understand  that  there 
is  the  same  increase  in  smooth  running  and  of  steady  power 
application  in  a  twelve-cylinder  engine  when  compared  with 
a  six-cylinder  or  an  eight-cylinder  engine.  It  was  just 
explained  that  with  an  eight-cylinder  engine  there  were 
four  explosions  per  revolution  of  the  crank  shaft.  In  a 


AUTOMOBILE  ENGINES 


39 


twelve-cylinder  engine  there  are  six  explosions  per  revolu- 
tion and  the  overlapping  of  power  strokes  is  still  more 
pronounced. 

Typical  Automobile  Engines.  One-,  two-,  and  three- 
cylinder  automobile  engines  are  now  so  infrequently  used 
that  no  space  need  be  given  to  their  description.  In  essen- 
tial parts  they  are  not  very  different  from  the  modern  types 
of  automobile  engines  with  more  cylinders.  Fig.  39  shows 


Legend 

Excess  Energy  abore 
Useful  Energy 
negative  Work 


Six  Cylinder  Engine 


jfisft 


.JLAAAJ 


Eight  Cylinder  Engine 

FIG.  38. — Relative  Flow  of  Power. 

a  typical  four-cylinder  engine  and  may  be  considered  repre- 
sentative of  standard  usage.  The  four  cylinders  are  arranged 
with  their  connecting  rods  attached  to  the  same  crank  shaft 
operating  in  a  single  enclosed  crank  case.  A  section  of 
the  crank  case  and  two  of  the  cylinders  are  shown  broken 
away  to  make  clear  the  attachment  of  the  connecting  rods 
to  the  crank  shaft.  The  first  cylinder  from  the  left  is  cut 
in  two  through  the  middle  to  show  the  construction  of  the 
piston,  connecting  rod  and  wrist  pin.  The  next  cylinder 
shows  only  the  cylindrical  section  cut-away  with  the  piston 


40 


GASOLINE  AUTOMOBILES 


and  connecting  rod  uncut.  The  third  cylinder  from  the  left 
is  sectioned  to  show  the  arrangement  of  the  valves.  A 
typical  six-cylinder  engine  is  shown  in  Figs.  40  and  41. 


Water  Jacket. 


....Water  Pipe 

....-Engine  Block 
-Coo  I  ing  Fan 


..Starting 
Crank 


.-Crank  Case 


Crank  Shaft  v-  Connecting  Rod 
FlG.  39. — Typical  Four-Cylinder  Automobile  Engine. 


Generator 
\Ignit/bn  Coif,  .' 


.ShrttrtqCrank- 
^ 


Oil  Pump     \ 
Crank  Case         Pump 


FIG.  40.  —  Typical  Six-Cylinder  Engine,  Showing  Water  Pump. 


Vacuum  Tank 
Water  Outte^  ;     ..-Manifold 

.Carbureter 


Clutch  Release  Shaft- 

FIG.  41. — Typical  Six-Cylinder  Engine,  Showing  Intake  Manifold 
and  Carbureter. 


AUTOMOBILE  ENGINES  41 

Figs.  42  and  43  show  typical  eight-cylinder  and  twelve- 
cylinder  engines  with  their  accompanying  equipment.  Note 
that  in  the  eight-cylinder  engine  there  is  an  angle  of  ninety 
degrees  between  the  two  rows  of  cylinders  whereas  twelve- 
cylinder  engines  are  made  with  an  angle  of  only  sixty 
degrees  between  the  rows.  Although  the  valves  are  arranged 
as  in  the  usual  L-head  cylinder  construction,  they  are  more 


FlG.  42.— Typical  Eight-Cylinder  Automobile  Engine. 

accessible  than  in  eight-cylinder  engines  because  of  the 
reduction  of  width  made  possible  by  placing  the  two  rows 
of  cylinders  with  angle  of  only  sixty  degrees  between  them. 
By  this  saving  in  width  of  the  engine,  the  electric  generator, 
the  starting  motor,  the  air  pump,  and  the  other  attachments 
can  be  mounted  at  the  side  of  the  crank  case  as  in  most 
four-cylinder  and  six-cylinder  engines.  One  method  of 
attaching  connecting  rods  to  the  crank  shaft  in  eight  and 
twelve-cylinder  engines  is  shown  in  Fig.  44. 


42 


GASOLINE  AUTOMOBILES 


The  Intake  Manifold.    In  an  automobile  engine  the  intake 
pipe    is    made    with    as   many    "branches"    as    there    are 


Cylinder 
y 


'arburerer 

Water  Jacketed 
Intake 
Manifold 


Cylinder 


Camshaft 


Connecting  Rod 
^-Crankshaft 

FIG.  43. — Typical  Twelve-Cylinder  Automobile  Engine. 


Oil  Wiper  King 
Connecting  Bod-Blade  Type 


meeting  Bod- Fork  Type 


FIG.  44. — Connecting  Kods  for  Eight  and  Twelve-Cylinder  Engines. 


AUTOMOBILE  ENGINES 


43 


cylinders.  These  "branches"  of  the  intake  pipe  are  called 
the  intake  manifold.  In  some  recent  engines  the  "branches" 
of  the  manifold  going  to  the  intake  valves  are  cast  in  the 
sides  of  the  cylinders.  The  advantage  of  this  construction 
is  that  the  manifold  can  be  kept  warm  by  the  heat  of  the 
engine  and  the  carbureter  can  be  placed  high  and  close  to 
the  cylinders. 

Power  Plant  Suspension.    In  nearly  all  recently  designed 


FlG.    45. — Four-point 
Suspension. 


FIG.    46. — Three-point 
Suspension. 


automobile  engines  the  clutch  and  speed-change  gears  are 
combined  with  the  engine  in  practically  a  continuous  casing 
in  such  a  way  as  to  form  what  we  call  a  single  power  plant 
unit.  This  "unit  construction"  has  the  advantage  of  retain- 
ing positively  the  alignment  of  the  shafts  in  the  speed-change 
gears,  under  most  conditions  of  operation.  This  method  of 
setting  up  the  engine,  clutch,  and  speed-change  gears  makes 
it  also  easy  to  apply  what  is  called  the  three-point  suspension. 


44 


GASOLINE  AUTOMOBILES 


In  some  automobiles  the  engine  and  speed-change  gear  case 
are  attached  to  the  automobile  frame  at  four  points — two  in 
the  front  and  two  near  the  middle  of  the  frame  as  in  Fig.  45. 
This  method  has  the  disadvantage  that  in  case  of  distortion 
of  the  frame  caused  by  operation  over  very  rough  roads,  or 
by  a  collision,  it  is  difficult  to  adjust  the  alignment  of  the 
engine  crank  shaft,  the  clutch  and  the  shafts  of  the  speed- 
change  gears,  so  that  there  would  not  be  excessive  wear  on 
the  several  parts.  Because  of  these  difficulties  the  three-point 
suspension  was  introduced.  This  method  of  suspension  means 
that  the  power  plant  unit  is  supported  as  in  Fig.  46  on  two 


Rear  Supports 
on  Side  Brackets 


Front  Power  Plant 
Support 


FIG.  47. — Three-point  Suspension  Applied  to  Dodge  Engine. 

points  in  front  and  one  point  near  the  speed-change  gears. 
In  the  Dodge  automobile  (Fig.  47)  the  three-point  suspen- 
sion is  reversed.  There  is  one  point  of  suspension  in  front 
and  two  other  supports  on  brackets  at  the  rear  end  of  the 
crank  case.  It  should  be  evident  that  with  the  three-point 
suspension  there  can  be  considerable  distortion  of  the  frame 
without  interfereing  with  the  correct  alignment  of  any  parts 
of  the  unit  power  plant. 

Engine  Cylinders.  Most  four-cylinder  and  six-cylinder 
engines  are  made  with  all  the  cylinders  in  a  single  casting. 
This  is  called  block  cylinder  construction.  It  makes  the  engine 


AUTOMOBILE  ENGINES  45 

considerably  shorter,  more  rigid,  and  lighter  than  if  there 
is  a  separate  casting  for  each  cylinder.  In  separate  cylinder 
construction  the  expense  for  renewal  of  a  cylinder  is  less  in 
case  it  is  broken  or  otherwise  damaged.  The  inside  diameter 
of  an  engine  cylinder  is  often  called  the  bore. 

Many  automobile  engines  are  made  with  detachable  cylinder 
heads  as  shown  in  Fig.  48.  This  construction  is  more  costly 
than  "solid"  cylinder  heads,  but  the  advantages  are  so 
apparent  that  it  is  coming  into  more  general  use.  It  is 
particularly  desirable  in  multiple  cylinder  engines,  like  eight- 
cylinder  and  twelve-cylinder  engines  in  which  there  are  a 
number  of  cylinders  to  be  cleaned. 

Worn  Cylinders.    In  much  used  engines  the  cylinder  may 

Removable  Head 


FIG.  48. — Detachable  Cylinder  Head  on  Block  Cylinders. 

be  worn  oval,  so  that  the  piston  and  its  rings  do  not  fit 
tightly.  When  the  cylinder  is  oval,  compression  is  weak 
and  the  piston  will  not  suck  in  the  mixture  properly. 
Furthermore,  when  the  explosion  occurs  much  of  the  burned 
gas  will  be  forced  past  the  pistons  down  into  the  crank 
case.  Improper  lubrication  is  a  common  cause  of  worn 
cylinders. 

Firing  Order.  In  conventional  four-cylinder  engines  the 
relative  positions  of  pistons,  connecting  rods,  and  crank 
shaft,  are  arranged  as  shown  in  Fig.  49.  In  this  figure  the 
main  bearings  and  the  connecting  rod  bearings  are  in  the  same 
vertical  plane  and  the  latter  are  marked  from  right  to  left 
with  the  numbers  1,  2,  3,  and  4.  Connecting-rod  bearings  1 
and  4  are  180  degrees  from  bearings  2  and  3 ;  so  that  the  pis- 


46  GASOLINE  AUTOMOBILES 

tons  1  and  4  are  always  in  the  same  up  or  down  position  in 
the  cylinders  at  any  instant,  but  for  different  services.  Thus, 
if  No.  1  piston  is  on  the  compression  stroke,  No.  4  piston 
will  be  on  the  exhaust  stroke.  At  the  same  time  No.  2 


FIG.  49.—  Crank  Shaft  for  Four-Cylinder  Engine. 

piston  will  be  on  the  suction  stroke  and  No.  3  piston  will 
be  on  the  explosion,  or  power,  stroke.  The  order  "of  firing" 
or  sequence  or  explosions  in  the  cylinders  is  in  this  case  1,  2, 


G 

FIG.  49A.  —  Typical  Crank  Shafts       FIG.  49B.  —  Typical  Crank  Shafts 
for  Four-Cylinder  Engines.  for  Six-Cylinder  Engines. 

4,  3.    In  a  four-cylinder  engine  the  firing  order  is  sometimes 
1,  3,  4,  2. 

The    cranks    of    a    six-cylinder    engine    are    placed    120 
degrees  apart  as  shown  in  Fig.  50.     Cranks  1  and  6,  2  and 

5,  3  and  4  move  together  in  pairs.    The  firing  order  is  usually 


AUTOMOBILE  ENGINES  47 

1,  5,  3,  6,  2,  4  for  the  first  shaft  shown  and  1,  4,  2,  6,  3,  5 
for  the  other. 

Horsepower  of  Automobile  Engines.  The  usual  method 
of  calculating  the  horsepower  of  automobile  engines  is  by 
the  use  of  the  8.  A.  E.  formula  (Society  of  Automotive  En- 
gineers). This  formula  is  intended  to  determine  only  approxi- 
mately the  useful,  or  brake  horsepower  (b.h.p.)  of  a  high 
speed  gasoline  engine.  Briefly, 

bore  in  inches  X  b°re  in  inches  X  number  cylinders 
horsepower  = _  . 


=st  r i ring  < 
I-4-2-6-31! 

TlG.  50. — Firing  Orders  in  Six-Cylinder  Engines. 

If  D  represents  the  diameter,  or  bore,  of  the  engine  cylinders 
in  inches,  and  N  represents  the  number  of  cylinders  in  the 
engine,  this  formula  is  stated  as  follows: 

D2N 

'  'P'=2lT=0' 

For  instance,  if  an  automobile  has  6  cylinders  and  the  bore 
is  4  inches,  the  horsepower  is, 

4  V  4  V  fi 

=38.4  horsepower. 


48  GASOLINE  AUTOMOBILES 

In  abbreviated  form  the  formula  may  be  used  as  follows: 

For     4  cylinder  engines,  b.h.p.  =  1.6JD* 

"       6        "              "  "      =2.41)* 

"8        "              "  "      =3.2D* 

"     12        "              "  " 


This  formula  gives  ratings  much  too  low  for  modern 
high-speed  automobile  engines,  but  gives  with  some  degree 
of  accuracy  the  maximum  horsepower  of  the  most  common 
makes  of  four-cylinder  engines,  which  are  not  intended  to  run 
at  more  than  about  1800  revolutions  per  minute.  Modern 
eight-  and  twelve-cylinder  engines  are  intended  to  operate 
at  least  fifty  percent  higher  piston  speeds  than  the  above 
formula  was  intended  to  cover.* 


*  Piston  displacement  is  a  term  sometimes  used  when  describing 
the  size  of  engine  cylinders.  It  depends  on  the  diameter  of  the  cylinder 
and  the  length  of  the  piston  stroke.  Literally  it  means  the  space  in  the 
cylinder  swept  through  by  the  piston  in  going  from  one  end  of  the 
stroke  to  the  other.  It  is  calculated  by  multiplying  the  area  of  a  circle 
of  the  diameter  of  the  inside  of  the  cylinder  in  square  inches  by  the 
length  of  the  piston  stroke.  The  displacement  is  in  cubic  inches.  The 
clearance  in  an  automobile  engine  is  the  space  inside  the  top  of  the 
engine  cylinder  which  the  piston  does  not 'enter. 


CHAPTER   III 
GASOLINE   AND    SUBSTITUTES 

Gasoline.  Nearly  all  automobiles. use  gasoline  for  engine 
fuel.  The  reason  is  that  it  vaporizes  more  easily  than  other 
similar  engine  fuels.  It  is  a  product  of  the  distillation  of 
crude  oil  (petroleum),  which,  when  heated  in  large  closed 
retorts  or  stills,  gives  off  vapor,  which  rises  from  the  oil. 
The  vapor  passes  from  the  top  of  the  retort  into  pipes  or 
cooling  coils  in  which  it  is  condensed.  In  this  process  of 
crude  oil  distillation,  the  lighter  vapors  like  gasoline, 
naphtha,  benzine,  etc.,  are  collected.  With  ordinary 
atmospheric  pressure  in  the  retort,  these  lighter  vapors  will 
be  obtained  when  the  crude  oil  is  heated  from  about  one 
hundred  to  one  hundred  twenty-five  degrees  Fahrenheit. 
If  considerable  pressure  above  atmospheric  is  maintained  in 
the  retort  by  an  air  pump,  the  lighter  vapors  can  be  dis- 
tilled off  (called  the  "cracking,"  "Burton,"  or  "Rittman" 
process)  when  the  temperature  is  very  much  increased  above 
the  limits  for  distillation  at  atmospheric  pressure. 

After  the  lighter  vapors  of  the  gasoline  variety  have 
been  collected  and  condensed,  if  heating  is  continued,  there 
is  further  rise  in  temperature  in  the  retort,  and  heavier 
vapors  are  collected  which,  when  condensed,  give  in  succes- 
sion, according  to  the  vaporizing  temperature,  kerosene, 
light  lubricating  ("engine")  oil,  fuel  oil  (for  steam  boilers), 
paraffine,  etc.  No  definite  percentages  can  be  stated  as  to 
the  relative  amounts  of  gasoline,  kerosene,  etc.,  from  such 
distillation,  for  much  depends  on  the  kind  of  crude  oil  used. 
Some  kinds  of  heavy  crude  oil  from  Middle  Western  and 
Western  States  give  relatively  little  gasoline  with  heating 
at  atmospheric  pressure,  but  considerable  amounts  with 
49 


50  GASOLINE  AUTOMOBILES 

pressure  distillation.  This  distillation  process  is  usually 
called  oil  refining. 

Kerosene  and  Alcohol.  For  the  same  reason  that  kero- 
sene does  not  vaporize  readily  in  the  distillation  process, 
it  is  difficult  to  use  it  in  automobile  engines  as  a  substitute 
for  gasoline,  which  is  easily  vaporized.  Alcohol  is  nearly 
as  difficult  to  vaporize  as  kerosene.  Neither  kerosene  nor 
alcohol  can  be  easily  vaporized  without  applying  heat,  and 
cannot,  therefore,  be  used  satisfactorily  for  starting  engines. 

Gasoline  Mixtures.  A  liquid  fuel  made  up  mostly  of  a 
mixture  of  alcohol  and  gasoline  has  some  advantages  as 
a  substitute  for  gasoline  in  engines.  It  is  a  well  known  fact 
that  the  efficiency  of  combustion  in  an  engine  can  be  con- 
siderably increased  by  going  above  the  present  limited  com- 
pression. When  gasoline  of  the  ordinary  commercial  quality 
is  used  in  an  engine,  the  compression  should  not  much  exceed 
seventy-five  pounds  per  square  inch  (gage)  pressure,  be- 
cause, at  a  higher  pressure,  an  explosive  mixture  of  gasoline 
and  air  is  likely  to  be  decomposed  by  the  heat  due  to  greater 
compression,  so  that  uncontrollable  combustion  results.*  It 
is  equally  well  known  that,  if  in  the  same  kind  of  engine, 
alcohol  is  used  for  fuel  instead  of  gasoline,  there  is  not  the 
same  limit  to  compression,  which  can  be  carried  to  a  much 
higher  pressure  without  serious  disadvantages. 

If  a  mixture  of  gasoline  and  alcohol,  in  about  equal  pro- 
portions, is  used  for  engine  fuel,  the  mixture  will  combine 
the  advantages  of  both.  The  gasoline  portion  will  vaporize 
readily  for  starting  the  engine  and  the  alcohol  will  make 
it  possible  to  use  much  higher  compression  pressures,  with 
the  advantages  of  higher  engine  efficiency.  Unless,  however, 
the  head  of  the  engine  piston  is  made  thicker,  so  as  to  reduce 
the  amount  of  space  in  the  top  of  the  engine  cylinder  provided 

*  The  allowable  limits  of  compression  for  very  high  grade  gasoline 
intended  for  high  compression  engines,  such  as  are  used  for  aeroplane 
service,  is  about  one  hundred  and  twenty-five  pounds  per  square  inch 
(gage).  Ordinary  compression  pressures  do  not  much  exceed  seventy 
to  seventy-five  pounds  per  square  inch. 


GASOLINE  AND  SUBSTITUTES  51 

for  the  compression  of  the  explosive  mixture,  the  advantages 
from  the  use  of  alcohol  will  not,  of  course,  be  obtained.  To 
use  mixtures  of  gasoline  and  alcohol  efficiently  the  compres- 
sion pressure  should  be  raised  to  at  least  double  the  pressure 
now  used.  A  recommended  gasoline  and  alcohol  mixture 
consists  of  forty  percent  alcohol,  forty  percent  gasoline,  and 
twenty  percent  benzol.  The  benzol  is  added  to  make  starting 
easier.  When  this  mixture  is  used  in  automobile  engines, 
there  is  practically  no  noticeable  knocking  in  the  engine  due 
to  the  high  compression.  Some  of  the  large  gasoline  selling 
stations  do  not  furnish  gasoline  but  instead  a  mixture  of 
heavy  gasoline  and  benzol,  which  is  a  first  class  engine  fuel 
and  is  usually  sold  a  little  cheaper  than  standard  gasoline. 
Such  mixtures  are  easily  recognized,  for  the  odor  is  unmis- 
takable and  is  different  from  that  of  gasoline.  For  winter 
service  not  much  benzol  can  be  used  in  gasoline  mixtures  as 
it  freezes  at  about  fifteen  degrees  Fahrenheit.  In  very  severe 
climates,  such  mixtures  might  freeze  solid  in  the  gasoline 
tank.  It  is  claimed  that  when  such  gasoline  mixtures  are 
used,  a  gasoline  engine  runs  more  smoothly  than  when 
ordinary  commercial  gasoline  alone  is  used.  Mixtures  of 
gasoline  and  benzol  are  commonly  called  "doped"  gasoline. 
The  addition  of  benzol  to  gasoline  gives  it  a  "sweet"  odor. 
Gasoline  made  by  the  cracking  process,  especially  if  it  has 
been  stored  a  long  while,  has  a  disagreeable  odor. 

The  principal  advantage  claimed  for  a  gasoline  and 
alcohol  mixture  is  that  the  maximum  power  of  an  engine 
is  increased  about  five  percent  with  the  usual  gasoline  com- 
pression, and  about  fifteen  percent  with  the  compression 
increased  to  about  one  hundred  and  fifty  pounds  per  square 
inch.  At  maximum  power,  the  fuel  consumption  per  brake 
horsepower,  when  a  mixture  of  gasoline  and  alcohol  is  used 
and  the  engine  is  operated  at  high  compression,  is  ten  percent 
less  than  with  gasoline  at  normal  engine  compression. 

Rate  of  Production  of  Gasoline.  The  present  production 
of  gasoline  is  nearly  two  gallons  for  every  automobile  in 
service  per  day.  With  between  2,000,000  and  3,000,000  new 


52  GASOLINE  AUTOMOBILES 

automobiles  and  tractors  put  on  the  market  each  year,  it 
is  likely  that  the  amount  which  can  be  allotted  for  each 
automobile  or  tractor  must  be  reduced  in  the  near  future. 

in  the  distillation  of  crude  oil,  between  twenty  and  twenty- 
five  percent  of  the  product  on  the  average  is  gasoline,  twelve 
percent  is  kerosene,  about  fifty  percent  is  fuel  oil,  and  the 
rest  is  lubricating  oil,  paraffin,  vaseline,  carbon,  etc.  About 
thirty  percent  of  the  gasoline  now  produced  comes  from 
the  portion  that  was  formerly  called  kerosene.  All  the  kero- 
sene cannot  be  taken  to  increase  the  gasoline  supply  because 
ninety  percent  of  the  world  is  still  lighted  with  kerosene 
lamps,  and  about  ninety-five  percent  of  the  world  does  not 
know  what  electric  lights  are.  The  kerosene  market,  there- 
fore, is  still  an  important  factor.  The  price  of  kerosene  will 
probably  soon  be  nearly  the  same  as  that  of  gasoline. 

Knocking  Caused  by  Engine  FueL  The  real  problem 
today  in  automobile  engineering  is  to  eliminate  the  carbon 
and  the  knocking  in  the  engine.  For  years  engineers  have 
been  trying  to  find  out  the  cause  of  knocking  in  gasoline 
engines  when  there  is  carbon  in  the  cylinders.  Knocking  in 
the  engine  cylinders  used  to  be  called  pre-ignition,  by  which 
is  meant  ignition  of  the  explosive  mixture  near  the  beginning 
of  the  compression  stroke,  thought  to  be  caused  by  red-hot 
particles  of  carbon  on  the  inside  surface  of  the  cylinders 
setting  the  explosive  mixture  afire  prematurely.  Chemical 
analysis  of  gasoline  shows  that  it  is  made  up  of  hydrogen 
and  carbon.  Now  when  gasoline  is  imperfectly  vaporized,  it 
breaks  up  and  bums  only  the  hydrogen.  The  carbon  is  left 
behind  to  settle  on  the  inside  surfaces  of  the  cylinders.  Carbon 
is  one  of  the  best  possible  heat  insulators.  "Wool  ranks  first 
as  a  heat  insulator,  and  finely  divided  carbon  is  second  of  the 
ordinary  materials.  As  long  as  the  temperature  of  combus- 
tion is  below  a  certain  point,  the  gasoline  will  burn  normally 
and  without  noise. 

If  the  temperature  of  the  incoming  air  is  reduced  to  ten 
degrees  below  the  Fahrenheit  zero,  an  engine  will  run  well 
on  kerosene  with  compression  at  eighty-five  pounds  per  square 


GASOLINE  AND  SUBSTITUTES  53 

inch.  The  refrigerated  air  simply  prevents  the  temperature 
of  combustion  from  going  above  the  critical  point  at  which 
the  kerosene  or  gasoline  breaks  up.  The  only  reason  a  gaso- 
line automobile  engine  runs  better  with  all  the  carbon  removed 
is  that  the  cooling  system  is  more  active  and  takes  away 
heat  rapidly  enough  at  the  time  of  highest  temperature  to 
keep  the  gasoline  from  breaking  up.  As  soon,  however,  as 
there  is  a  little  deposit  of  carbon,  the  cooling  system  is  not 
so  active  and  the  temperature  gets  too  high.* 

If  the  temperature  of  combustion  is  kept  from  rising 
above  the  point  at  which  the  gasoline  breaks  up,  perfect 
combustion  is  possible  and  gasoline  engines  will  run  without 
carbon  accumulations  and  without  knocking  in  the  cylinders. 

Regulating  Combustion  by  Additions  to  the  Fuel.  A 
small  quantity  of  ordinary  aniline  added  to  the  gasoline  used 
in  a  gasoline  engine  will  entirely  change  its  operation.  The 
addition  of  only  one  percent  of  aniline  to  the  gasoline  used 
in  an  automobile  engine  which  does  not  travel  well  on  steep 
hills  and  is  troublesome  on  account  of  knocking  will  change 
the  running  of  the  engine  to  give  almost  perfect  operation. 
Schroeder,  when  he  tried  to  make  his  great  altitude  flights 
in  1919,  at  first  reached  only  32,000  feet  and  could  go  no 
higher  with  ordinary  gasoline.  Later,  he  mixed  two  or  three 
percent  of  aniline  with  the  gasoline  and  went  up  for  a  record- 
breaking  flight,  and  had  no  trouble  with  the  explosive  mixture. 

The  increase  in  gasoline  supply  must  come  from  the 
present  ''fuel"  part  of  crude  oil,  which  is  now  about  fifty 
percent.  At  least  eighty  percent  of1  this  can  be  refined  into 


*  This  temperature  change  is  relatively  large  for  a  slight  change  in 
cooling,  because  the  specific  heat  of  the  gases  is  so  low;  that  is,  the 
amount  of  heat  which  is  required  to  raise  a  volume  of  gas  through  a 
degree  is  so  low  that  just  a  little  more  energy,  plus  or  minus,  means  a 
great  raising  or  lowering  of  the  temperature  curve,  and  a  few  heat  units 
added  to  the  gas  will  raise  the  temperature  many  degrees.  When  the 
temperature  reaches  the  point  where  gasoline  breaks  up,  the  combustion 
is  fifty  or  sixty  times  as  fast  as  in  a  normal  explosion,  and  it  is  the  im- 
pact of  this  violent  explosion  that  causes  knocking  in  the  engine. 


54  GASOLINE  AUTOMOBILES 

water-white  oil  resembling  kerosene,  which  makes  an  excellent 
engine  fuel,  if  used  in  such  a  way  as  to  prevent  the  breaking 
up  of  the  fuel. 

Aniline,  iodine,  or  some  other  similar  ingredient,  when 
mixed  with  gasoline,  will  break  up  at  a  lower  temperature 
than  the  gasoline,  and  by  thus  absorbing  heat  energy  it  keeps 
down  the  temperature  of  the  gasoline.  For  example,  if  a 
mixture  of  water  and  alcohol  is  put  on  a  stove,  the  tempera- 
ture of  the  water  cannot  be  raised  while  any  alcohol  remains, 
because  the  alcohol  will  evaporate  and  keep  the  temperature 
down.  Aniline  breaks  up  at  about  one  thousand  or  eleven 
hundred  degrees  Fahrenheit,  and  in  the  process  of  breaking 
up  absorbs  considerable  heat. 

If  the  automobile  manufacturers  could  get  the  chemical 
industry  to  increase  the  coal  tar  production  of  the  country, 
so  that  aniline  could  be  sold  at  two  dollars  per  gallon,  it 
would  not  be  too  expensive  for  general  use.  If  the  use  of 
such  gasoline  and  aniline  mixtures  became  common,  the  com- 
pression of  automobile  engines  could  be  safely  raised  to  one 
hundred  pounds  per  square  inch,  which  would  almost  double 
the  efficiency  of  normal  running.  Automobile  engineers  pre- 
dict that  within  five  years  gasoline  engines  will  run  inde- 
finitely without  any  carbon  trouble  on  almost  any  kind  of 
petroleum  fuel.  Even  if  the  addition  of  antiknocking 
chemicals  increases  the  cost  of  gasoline  two  or  three  cents 
per  gallon,  the  method  would  be  economical  because  of  the 
saving  of  fuel  and  of  the  cost  of  carbon  removal. 

Hydrometers.  In  order  to.  determine  the  quality  of  gaso- 
line, as  to  whether  it  is  a  light  or  a  heavy  grade,  a  sample 
may  be  conveniently  tested  with  a  small  glass  instrument 
called  a  hydrometer.  A  typical  hydrometer  is  shown  in  Fig. 
51,  as  it  appears  when  immersed  in  gasoline  and  in  kerosene. 
There  are  etched  numbers  on  the  stem,  reading  upward.  These 
numbers  on  a  hydrometer  for  gasoline  testing  are  called 
degrees  of  Baume  test,  named  for  the  man  who  introduced 
this  method  of  testing.  These  Baume  or  hydrometer  degrees 
have  no  relation  to  degrees  of  temperature.  A  hydrometer 


GASOLINE  AND  SUBSTITUTES 


55 


placed  in  a  vessel  containing  liquid  like  gasoline  sinks  to 
a  depth  corresponding  to  the  density  of  the  liquid.  It  sinks 
deeper  in  light  gasoline  than  in  heavy  oil.  The  reading  is 
taken  on  the  etched  scale  at  the  surface  of  the  liquid.  The 
heavier  the  liquid,  the  lower  the  reading  will  be ;  thus,  gaso- 
line testing  fifty  degrees  is  much  heavier  and  more  difficult 
to  vaporize  than  that  testing  sixty  degrees.  It  is  easy  to 


Fis.  51. — Hydrometer. 

remember  that  0.70  specific  gravity  is  approximately  the  same 
at  70  degrees  on  the  Baume  scale. 

There  is  not  much  difference  in  the  heating  or  "power" 
value  of  the  different  kinds  of  gasoline  per  pound;  that  is, 
a  pound  of  gasoline  will  give  about  the  same  amount  of 
heating  value  irrespective  of  the  source  of  the  crude  oil 
from  which  it  was  distilled  or  of  the  process  of  distillation. 
But  low  test  (heavy)  gasoline  has  more  pounds  to  the  gallon 
than  high  test  (light)  gasoline,  so  that  measured  in  gallons — 


56  GASOLINE  AUTOMOBILES 

assuming,  of  course,  equally  good  vaporization  and  combus- 
tion— low  test  gasoline  will  take  an  automobile  farther  per 
gallon  than  the  high  test  kind. 

Gasoline  Tanks.  Gasoline  for  use  in  automobile  engines 
is  usually  carried  in  a  tank  holding  from  ten  to  twenty 
gallons,  placed  in  most  automobiles  at  the  rear  between  the 
back  springs,  but  there  are  some  automobiles  with  high-hung 
bodies  in  which  the  gasoline  tank  is  placed  under  the  front 
seat,  and  in  still  others,  under  the  dash  behind  the  engine. 
In  the  most  common  system  of  gasoline  supply,  which  is,  in 
fact,  used  in  at  least  eighty  percent  of  the  automobiles  with 
rear  tanks,  the  principle  of  vacuum  or  suction,  as  explained 
in  the  following  paragraphs,  is  applied  to  bring  the  gasoline 
to  the  engine. 

Vacuum  Gasoline  Feed  System.  A  commonly  used  device 
to  draw  gasoline  from  a  tank  located  below  the  level  of  the 
carbureter  is  the  Stewart  vacuum  apparatus  shown  in  Fig. 
52.  The  method  of  attachment  of  this  system  in  an  automo- 
bile is  shown  in  Fig.  53.  The  auxiliary  tank  is  placed  higher 
than  the  intake  pipes  of  the  engine  so  that  it  is  necessary 
to  draw  the  gasoline  into  it  from  the  main  tank  by  suction. 
The  suction  of  the  automobile  engine  is  used  to  draw  the 
gasoline  from  the  main  tank  at  the  rear  of  the  automobile 
to  the  auxiliary  tank,  which  acts  really  as  a  vacuum  pump. 
From  the  auxiliary  tank  the  gasoline  flows  to  the  engine  by 
gravity.  By  this  system  all  the  advantages  of  a  simple  gravity 
system  as  explained  later  are  obtained  with  a  relatively  simple 
apparatus,  which  is  usually  mounted  in  front  of  the  dash, 
at  one  side  of  the  engine.  There  must  be  a  small  vent  hole 
in  the  filling  plug  of  the  main  tank  at  the  rear  so  that  the 
pressure  inside  that  tank  will  be  atmospheric. 

The  auxiliary  vacuum  tank  is  divided  into  two  chambers ; 
the  upper  one  is  the  filling  chamber,  marked  F.  The  lower 
one  is  the  emptying  chamber  E.  The  two  chambers  are 
separated  by  a  diaphragm  which  has  a  downward  projecting 
spout  P.  The  upper  chamber  has  a  float  L,  which  controls 
the  valves  D  and  U.  The  gasoline  pipe  8,  running  to  the 


GASOLINE  AND  SUBSTITUTES 


57 


main  tank  at  the  rear  of  the  automobile,  discharges  into 
the  upper  chamber  F.  An  air  pipe  T  extends  from  the  top 
of  this  chamber  to  the  intake  pipe  of  the  engine;  the  engine 
suction  for  drawing  the  gasoline  from  the  rear  tank  is  exerted 
through  this  pipe.  The  lower  chamber  is  used  to  supply 


FIG.   52. — Vacuum  Gasoline  Feed  Tank. 

gasoline  to  the  engine  by  gravity,  and  must  be,  therefore, 
under  atmospheric  pressure  at  all  times  so  that  the  flow  from 
it  through  the  pipe  0  to  the  carbureter  will  be  continuous. 
Since  the  bottom  of  this  gravity  chamber  is  located  at  a 
higher  level  than  the  carbureter  on  the  engine,  there  will 
always  be  a  free  flow  of  gasoline  as  long  as  this  tank  is  kept 


58  GASOLINE  AUTOMOBILES 

filled.  The  pipe  A,  which  at  its  lower  end  enters  the  lower 
chamber,  has  always  a  free  opening  to  atmospheric  pressure. 
Similarly  there  is  atmospheric  pressure  in  the  pipe  B,  for  it 
is  open  to  the  air  at  the  top  of  the  curved  end.  The  above 
explanation  shows  the  principle;  but  as  the  auxiliary  or 
vacuum  tank  is  usually  constructed  the  upper  chamber  sets 
into  the  lower  chamber,  forming  an  inner  wall  and  an  outer 
wall  at  the  upper  part  of  the  tank.  (Fig.  54.)  Between  these 
two  walls  is  left  a  narrow  air  space,  which  permits  air  to  flow, 
through  a  vent  in  the  top  of  the  tank,  down  into  the  lower 
chamber.  By  this  method  the  lower  chamber  is  kept  always 
at  atmospheric  pressure  without  the  use  of  such  a  pipe  as 
A  in  Fig.  52. 


Intake  Manifold 

rsruum  Tank 


FIG.  53.— Vacuum  System  of  Gasoline  Supply. 

In  order  to  suck  gasoline  from  the  main  tank,  which  is 
at  a  lower  level,  into  the  upper  chamber,  the  suction  valve 
U  at  the  bottom  of  the  pipe  T  must  be  opened,  and  the  atmos- 
pheric valve  D  at  the  bottom  of  the  pipe  B  must  be  closed. 
In  this  operation  one  goes  up  and  the  other  goes  down. 
Under  these  conditions  the  float  L  is  at  the  bottom  of  the 
upper  chamber  and  a  vacuum  is  produced  in  this  chamber 
by  the  suction  of  the  engine,  transmitted  through  its  intake 
pipe  T.  The  vacuum  in  the  upper  chamber  then  draws  the 
gasoline  from  the  main  supply  line.  As  the  upper  chamber 
fills,  the  float  rises  until  it  gets  near  the  top  when  it  closes 
the  suction  valve  U,  and  opens  the  atmospheric  valve  D. 
After  this  movement  of  the  float  valves,  there  will  be  atmos- 
pheric pressure  in  the  upper  chamber  as  well  as  also  in  the 


GASOLINE  AND  SUBSTITUTES 


59 


lower  chamber,  and  the  gasoline  will  flow  by  gravity  from 
one  chamber  into  the  other  through  the  vertical  spout  P.  The 
flat  valve  V  is  put  at  the  bottom  of  the  vertical  spout  to 
prevent  the  gasoline  in  the  lower  chamber  from  being  sucked 
back  into  the  upper  one  when  the  suction  valve  is  open.  The 
valve  U  on  the  suction  pipe  T,  leading  to  the  intake  pipe 
of  the  engine,  and  the  valve  D  on  the  air  vent  are  controlled 


Air  Vent—., 


To  Carbureter 

FIG.  54. — Stewart  Vacuum  Tank. 

by  levers,  which  are  pivoted  at  G  with  their  outer  ends 
connected  by  coil  springs,  as  shown.  These  springs  are 
arranged  so  that  the  float  L  is  normally  held  near  its  highest 
position,  and  will  be  raised  only  a  little  when  the  level  of 
the  liquid  rises  high  enough  to  elevate  it  farther.  It  is  clear, 
therefore,  that  the  float  cannot  take  an  intermediate  position 
and  the  action  of  the  upper  chamber  as  a'  vacuum  pump  is, 
therefore,  intermittent  and  not  gradual  and  continuous.  This 
kind  of  intermittent  action  is  necessary  in  order  that  the 


60  GASOLINE  AUTOMOBILES 

upper  chamber  may  be  under  atmospheric  pressure  part  of 
the  time,  when  the  gasoline  will  flow  by  gravity  from  the 
upper  chamber  to  the  lower.  When  the  level  of  the  gasoline 
drops  to  a  certain  point,  the  float  L  drops  slightly  from  its 
elevated  position,  and  by  its  movement  opens  the  valve  U 
on  the  suction  line  and  closes  the  valve  D  on  the  atmospheric 
line.  With  the  valves  in  this  position,  the  suction  of  the 
engine  again  causes  a  flow  of  gasoline  from  the  main  supply 
tank.  As  soon  as  the  level  of  the  gasoline  rises  so  as  to 
elevate  the  float,  the  valves  have  the  opposite  movement,  which 
closes  the  suction  pipe  and  opens  the  air  vent. 

Sometimes  it  happens,  if  an  automobile  is  allowed  to  stand 
for  a  long  time  with  the  engine  shut  off,  that  because  of  a 
leakage  in  the  system,  the  vacuum  tank  becomes  empty.  But 
this  tank  can  usually  be  filled  again  with  enough  gasoline 
for  starting  when  the  engine  is  turned  over  four  or  five 
revolutions  with  the  throttle  valve  completely  closed.  A  metal 
screen  is  put  at  the  end  of  the  gasoline  supply  line  8,  near 
where  it  enters  the  vacuum  tank,  to  prevent  sediment  or 
foreign  material  from  entering  the  float  chamber. 

An  emergency  filling  plug  Q,  when  unscrewed  and  taken 
out,  makes  it  possible  to  pour  gasoline  through  the  hole  from 
which  the  plug  is  taken.  For  this  filling  a  small  funnel 
should  be  used.  At  other  times,  this  plug  should  be  screwed 
tightly  so  that  there  can  be  no  air  leakage  into  the  upper 
chamber,  for  air  leakage  would  prevent  the  drawing  of 
gasoline  from  the  main  tank  by  engine  suction.  For  cold 
weather  service,  this  system  has  the  advantage  that  the 
auxiliary  tank  is  near  the  engine  and  the  gasoline  going 
through  it  will  be  heated  on  the  way  to  the  carbureter;  in 
this  way,  vaporization  is  improved. 

Sometimes  the  float  L  will  leak  and  fill  with  gasoline.  If 
it  does  the  valves  U  and  D  will  not  operate,  and  there  will 
be  continuous  suction,  so  that  the  two  chambers  will  fill  com- 
pletely with  gasoline,  and  finally  the  pipe  leading  to  the  intake 
of  the  engine  will  be  partly  filled.  The  engine  will  then 
get  a  mixture  much  too  rich  in  gasoline  for  good  operation. 


GASOLINE  AND  SUBSTITUTES  61 

In  that  case,  the  cover  of  the  tank  (Fig.  55)  should  be 
taken  off  at  the  top  so  that  the  float  can  be  taken  out 
and  repaired.  If  this  trouble  with  the  float  should  occur 
when  the  automobile  is  "on  the  road,"  it  is  best  to  take 
off  the  cover  very  carefully,  fill  the  tank  with  gasoline, 
and  then  replace  the  cover  loosely.  The  auxiliary  tank  will 
then  be  used  as  a  gravity  tank.  When  the  tank  is  empty, 
the  cover  can  be  taken  off  and  the  tank  refilled. 

Gravity  Gasoline  Feed  System.  The  gravity  system  of 
gasoline  supply  consists  simply  of  a  gasoline  tank  under 
one  of  the  seats  of  the  automobile  and  a  pipe  for  carrying 
the  gasoline  by  gravity  or  by  its  own  weight  to  the  car- 
bureter. Under  the  tank  there  is  a  sediment  chamber.  Dirt 


FIG.  55. — Top  of  Stewart  Tank. 

and  water  being  heavier  than  gasoline  will  settle  at  the 
bottom  and  can  be  cleaned  out  through  the  pet  cock.  Water 
is  apt  to  accumulate  in  the  bottom  of  the  tank,  and,  if  it 
freezes  in  cold  weather,  the  gasoline  supply  may  be  shut 
off.  If  this  happens,  it  is  wiser  to  put  hot  cloths  on  the 
bottom  of  the  tank  and  on  the  gasoline  pipe  rather  than 
to  take  the  risk  of  using  a  flame  for  heating. 

Pressure  Gasoline  Feed  System.  Another  system  used 
is  the  pressure  system.  Not  many  automobiles  use  this 
system;  but  some  of  the  most  expensive  automobiles  are 
equipped  this  way.  The  tank  is  at  the  rear  of  the  auto- 
mobile, as  it  is  in  the  Stewart  vacuum  system,  but  with 
the  difference  that  it  is  air  tight.  The  Packard,  Pierce, 
and  Locomobile  makes  still  have  this  system.  The  cap  of 


62  GASOLINE  AUTOMOBILES 

the  gasoline  tank  must  be  screwed  on  tightly  because  air 
pressure  on  the  top  of  the  gasoline  in  the  tank  forces  the 
gasoline  into  the  carbureter.  A  small  air  pump,  driven  by 
the  engine,  delivers  air  under  pressure  through  a  pipe  enter- 
ing the  top  of  the  gasoline  tank. 

After  an  automobile  has  been  standing  several  hours, 
there  will  not  be  enough  pressure  in  the  tank  to  force  the 
gasoline  into  the  carbureter ;  and  then  a  hand  pump,  intended 
for  emergency  use  and  placed  near  the  driver's  seat,  is  used 
to  provide  enough  pressure  for  starting;  but  it  is  necessary 
first  to  open  a  valve  below  this  pump,  so  that  the  air  can 
be  pumped  into  the  tank.  Usually  the  handle  of  a  valve 
on  any  automobile  hangs  down  when  the  valve  is  closed. 

Leaks  in  Air  Lines.  If  there  is  a  slight  leak  in  any  part 
of  an  air  line  for  pressure  or  vacuum,  the  gasoline  supply 
to  the  carbureter  will  probably  be  stopped.  Do  not  test 
for  air  leaks  by  holding  a  match  to  the  leak.  That  is  too 
dangerous  around  an  automobile.  It  is  best  to  take  a  little 
soapy  water  and  put  it  on  the  places  where  there  are  likely 
to  be  leaks.  Bubbles  will  then  form  at  the  leak.  Chewing 
gum  or  shellac  may  be  put  over  air  leaks  until  the  automobile 
can  be  taken  to  a  repair  shop. 


CHAPTER   IV 
GASOLINE    CARBURETERS 

A  carbureter  is  a  device  used  for  (1)  vaporizing  gasoline 
and  then  (2)  mixing  the  vaporized  gasoline  with  a  suitable 
amount  of  air.  When  the  proportions  of  gasoline  vapor 
and  air  used  in  a  gasoline  engine  are  in  correct  proportions 
there  will  be  high  power  explosions  in  the  engine  cylinders. 
If  there  is  too  much  gasoline  in  proportion  to  air  there 
will  be  imperfect  explosions,  indicating  incomplete  combus- 
tion, and  black  smoke  will  be  observed  coming  through  the 
exhaust  pipe.  On  the  other  hand,  if  there  is  too  much  air, 
there  will  be  little  power  and  troublesome  carbureter  opera- 
tion. Right  mixture  proportions  give  the  sharpest  and  the 
most  efficient  explosions,  because  the  combustion  of  all  the 
gasoline  takes  place  at  the  proper  time  and  leaves  no  un- 
burned  parts  to  be  wasted. 

Principle  of  Carbureter  Action.  The  principle  of  suction 
is  fundamental  in  all  modern  carbureters  for  automobile 
engines.  This  principle  can  be  simply  demonstrated  by  put- 
ting one  end  of  a  small  glass  tube  in  a  cup  of  gasoline  and 
sucking  at  the  other  end  so  that  gasoline  is  drawn  up  into 
the  tube.  How  far  up  the  gasoline  level  stands  in  the  tube 
depends  on  the  suction.  The  same  suction  effect  would  be 
observed  if  a  mechanical  apparatus  for  pumping  air  were 
attached  to  the  top  of  the  glass  tube.  Now  consider  what 
happens  in  an  automobile  engine  cylinder  when  a  pipe,  which 
dips  into  a  cup  of  gasoline,  is  attached  to  the  intake  valve 
of  the  engine.  During  the  suction  stroke  when  the  piston 
is  moving  downward  with  the  exhaust  valve  closed  and 
the  intake  valve  open,  the  necessary  suction  is  produced  to 
suck  gasoline  vapor  through  the  pipe  and  the  intake  valve 


GASOLINE  AUTOMOBILES 


into  the  engine  cylinder.  An  intake  pipe  for  this  purpose 
might  be  arranged  with  two  branches  as  shown  in  Fig.  56, 
one  of  which  dips  into  gasoline  and  the  other  is  open  to 
the  air.  By  means  of  such  a  device  the  suction  of  the  engine 
piston  will  suck  a  mixture  of  gasoline  and  air  into  the 
cylinder.  This  device  suggests  one  way  to  put  an  explosive 


'Spark  Plug 


Exhaust 
Valve  -E 


Intake 
Valve-/ 


FIG.  56. — Simple  Carbureter. 

mixture  into  the  engine  cylinder.  It  is  a  kind  of  carbureter. 
All  gasoline  carbureters  have  similarly  branched  passages 
although  not  so  simply  arranged.  Through  one  branch  air 
is  drawn,  and  through  the  other  gasoline  vapor. 

Unless  the  supply  of  liquid  gasoline  is  arranged  to  give 
a  practically  constant  level  in  the  gasoline  cup  (Fig.  56), 
the  flow  of  gasoline  vapor  into  the  intake  pipe  of  the  engine 
will  be  irregular.  If  the  gasoline  level  is  lowered,  the  gaso- 
line must  be  sucked- up  a  greater  distance  and  the  engine 


GASOLINE  CARBURETERS 


65 


suction  will  draw  less  into  the  cylinder.    On  the  other  hand, 
if  the  level  is  raised,  it  will  draw  more. 

Spray  Nozzles.  In  nearly  all  types  of  commercial  car- 
bureters some  kind  of  spraying  device  is  used  for  vaporizing 
the  gasoline.  In  such  a  device  the  gasoline  is  discharged 
as  a  spray  from  a  nozzle  located  in  a  suitable  passage  where 
the  sprayed  gasoline  vapor  will  be  easily  mixed  with  air. 
An  upward  current  of  air  passing  around  a  small  nozzle 
like  N  in  Fig.  57  has  enough  suction  effect  to  draw  out  the 
gasoline  even  when  the  level  of  the  gasoline  is  slightly  below 
the  top  of  the  nozzle.  The  figure  shows  the  level  in  the 
nozzle  the  same  as  in  the  reservoir  R. 


FIG.  57. — Simple  Nozzle 
Carbureter. 


FIG.  58. — Nozzle  Carbureter 
with  Pistoa  Suction. 


Actual  vaporization  as  accomplished  with  a  spray  nozzle 
carbureter  will  be  described  more  in  detail  with  the  help  of 
Fig.  58.  This  figure  shows  a  spray  nozzle  N,  an  air  passage 
A,  a  cylinder  or  mixing  chamber  M,  and  a  piston  P  with  a 
handhold  H.  The  gasoline  level  in  the  nozzle  is  shown  higher 
than  in  the  reservoir  R,  as  it  would  be  (1)  on  account  of 
the  upward  air  current  causing  a  slight  suction  over  the 
nozzle,  and  (2)  on  account  of  the  suction  produced  when 
the  piston  P  is  raised  upward  in  the  air-tight  cylinder  M 
as  indicated  by  the  arrow.* 


*  With    air    velocity    through    the    passage    A    at    about    the    usual 
velocities  in  a  commercial  type  of  carbureter  using  gasoline,  there  may 


06  GASOLINE  AUTOMOBILES 

Float  Regulator.  A  device  for  regulating  the  amount 
of  gasoline  going  into  the  reservoir  R  in  a  carbureter  like 
Fig.  58  is  necessary  if  the  gasoline  is  to  be  at  constant  level. 
For  this  purpose  a  float  is  connected  to  a  small  valve,  called 
a  float  valve,  which  shuts  off  the  flow  from  the  gasoline  supply 
pipe.  The  float  device  is  self-adjusting  and  the  valve  con- 
nected to  the  float  shuts  off  the  flow  of  gasoline  when  the 
level  in  the  reservoir  rises  nearly  to  the  top  of  the  nozzle.  A 
carbureter  could  be  made  to  operate  with  the  float  arranged 
to  have  the  established  level  of  the  liquid  as  high  as  the 
top  of  the  nozzle,  but  the  float  is  always  set  to  shut  off  at 
a  lower  level  so  that  there  will  be  a  margin  of  safety  in  case 
of  inaccurate  or  sluggish  operation  of  the  float  and  valve, 
which  might  cause  an  excessive  flow  of  gasoline  from  the 
nozzle.  Even  with  the  best  devices  this  sometimes  happens 
when  the  float  or  valve  "sticks"  and  allows  the  gasoline  to 
rise  in  the  float  chamber  slightly  above  the  established  level 
so  that  it  overflows  from  the  nozzle.  A  low  gasoline  level 
in  the  nozzle  atso  prevents  dripping  from  the  nozzle  when 
the  engine  is  "idle"  and  is  not  in  a  level  position,  or  when 
excessive  vibration  might  cause  the  gasoline  to  overflow  into 
the  air  passage  A. 

Float-Feed  Carbureter.  Fig.  59  shows  a  very  simple  type 
of  carbureter  in  which  the  flow  or  "feed"  of  gasoline  is 
regulated  by  a  float  F.  The  liquid  fuel  supply  enters  at  G 
and  flows  through  the  float  valve  FV  into  the  float  chamber  C, 
from  which  some  of  the  gasoline  flows  into  the  tube  U  leading 
to  the  spray  nozzle  N.  When  the  gasoline  level  in  the  float 
chamber  rises  and  is  only  about  one-sixteenth  inch  from  the 
top  of  the  spray  nozzle  the  float  closes  the  attached  valve  FV, 

be  a  considerable  difference  in  level  between  the  top  of  the  nozzle  and 
the  surface  of  the  liquid  in  the  reservoir  B  before  the  gasoline  spray 
ceases.  It  may  be  as  much  even  as  one  and  one-half  inches,  and  with 
a  flow  of  gasoline  once  established  the  spray  will  usually  continue  until 
the  difference  in  level  is  as  much  as  two  inches.  These  unusual  condi- 
tions result  sometimes  when  the  gasoline  supply  for  an  engine  is  nearly 
exhausted. 


GASOLINE  CARBURETERS 


67 


and  prevents  the  gasoline  from  rising  higher.  The  air  supply 
enters  through  the  passage  A  and  passes  up  in  the  direction 
of  the  arrow  into  the  mixing  chamber  M ,  where  the  air  mixes 
with  the  gasoline  vapor  discharging  from  the  spray  nozzle  N. 
The  top  of  the  mixing  chamber  M  is  made  so  that  there  will 
be  air  tight  connections  to  the  intake  pipe  of  the  engine.* 
The  engine  piston  on  its  suction  or  intake  stroke  produces 
the  necessary  suction  to  draw  the  explosive  mixture  of  gasoline 
vapor  and  air  from  the  mixing  chamber  into  the  engine 
cylinder. 


FIG.  59. — Simple  Carbureter 
with  Float  Feed. 


FIG.  60. — Carbureter  with 
Auxiliary  Air  Valve. 


In  the  operation  of  the  carbureter,  the  removal  of  gasoline 
through  the  nozzle  N  lowers  the  level  in  the  float  chamber  C 
and  causes  the  float  F  to  descend  enough  to  open  the  float 
valve  FV,  which  allows  more  gasoline  to  enter.  In  this  way 
a  nearly  constant  level  can  be  maintained  in  the  float  chamber 
and  also  in  the  spray  nozzle. 

Auxiliary  Air  Valve.  When  the  speed  of  an  engine 
increases,  the  suction  produced  by  the  piston  in  the  intake 
pipe  increases  in  proportion.  Increased  suction  will  propor- 
tionally increase  the  amount  of  gasoline  sucked  out  of  the 
spray  nozzle  of  the  carbureter.  On  the  other  hand,  increased 


*  The  float  chamber  should  not  be  made  air  tight  where  the  rod  B 
connecting  the  float  with  the  float  valve  FV  passes  through  the  cover 
plate  L. 


68  GASOLINE  AUTOMOBILES 

suction  does  not  increase  proportionally  the  amount  of  air 
passing  through  the  air  passage.  Gasoline  is  a  liquid  and 
its  particles  "hang  together,"  when  pulled  by  suction;  but 
air  is  an  elastic  and  "expansive"  fluid  with  no  tendency  for 
the  particles  to  "hang  together."  Because  of  this  difference, 
the  amounts  of  air  and  of  gasoline  sucked  into  a  carbureter 
are  not  in  the  same  proportions  at  different  engine  speeds. 
For  example,  an  average  size  of  automobile  engine  will  take 
in  through  the  carbureter  about^  fifty  pounds  of  air  and  five 
pounds  of  gasoline  per  hour  when  running  at  a  speed  of  five 
hundred  revolutions  per  minute.  If  the  speed  is  increased  to 
one  thousand  revolutions  per  minute,  the  amount  of  gasoline 
will  be  ten  pounds  (increased  in  proportion  to  the  speed) ; 
but  the  amount  of  air  will  be  only  about  eighty  pounds  instead 
of  one  hundred  pounds  as  it  would  be  if  the  amount  of  air 
increased  in  proportion  to  the  speed.  If  the  parts  of  the 
simple  form  of  carbureter  already  explained  will  give  an 
efficient  mixture  of  gasoline  and  air  at  an  engine  speed 
of  five  hundred  revolutions,  the  mixture  will  not  be  right 
at  one  thousand  revolutions  per  minute^  In  other  words, 
at  the  higher  speeds,  the  mixture  will  be  too  "rich"  in  gaso- 
line. Also,  if  the  mixture  is  right  for  high  speeds  it  will  be 
wrong  for  low  speeds.  All  simple  carbureter  devices  like 
the  one  shown  in  Fig.  59  will  give  the  engine  an  explosive 
mixture  richer  in  gasoline  when  air  passes  around  the  spray 
nozzle  at  high  velocity  and  high  suction  than  when  at  low  ' 
velocity  and  low  suction.  (  In  other  words,  increasing  the 
engine  speed  increases  also  the  percentage  of  gasoline  in  the 
explosive  mixture.  All  kinds  of  spray  nozzle  carbureters 
must,  therefore,  use  some  adjusting  device,  which  should  be 
automatic.  Such  a  device  is  called  an  auxiliary  air  valve  \ 
of  which  a  typical  example  is  marked  AV  in  Fig.  60^  This  \ 
auxiliary  air  valve  is  provided  with  a  spiral  spring  X  of 
sufficient  strength  to  hold  it  closed  at  low  engine  speeds, 
when  there  is  little  suction  in  the  mixing  chamber  M.  In- 
creased engine  speed  produces  greater  suction  so  that  this 
valve  will  be  opened  varying  amounts  in  proportion  to  the 


GASOLINE  CARBURETERS  69' 

speed.  It  will  be  open  a  little  at  moderate  speeds,  and  more 
at  high  speeds,  permitting  additional  air  flow  into  the  mixing 
chamber  M.  This  additional  air  supply,  as  the  speed  of  the 
engine  is  increased,  has  the  effect  of  reducing  the  suction 
in  the  air  passage  A  in  proportion  to  the  amount  of  opening 
of  the  valve.  A  plug  K  at  the  bottom  of  the  float  chamber 
can  be  removed  for  cleaning  out  water  and  dirt  carried  in 
from  the  gasoline  supply  pipe  G.  A  small  cock  H  is  at  the 
bottom  of  the  spray-nozzle  tube  which  is  intended  for  the 
rapid  removal  of  any  accumulation  of  water  or  for  tapping 
small  quantities  of  gasoline  from  the  carbureter  for  engine 
priming,  cleaning,  etc.  — 

Priming  a  Carbureter.  An  explosive  mixture,  very  rich 
in  gasoline  is  usually  necessary,  especially  in  cold  weather, 
to  start  a  gasoline  engine.  Conditions  for  combustion  are 
very  unfavorable  when  the  engine  is  cold  and  when  it  is 
turning  over  slowly  for  starting.  One  reason  is  that  there 
is  a  leakage  of  the  compression  pressure  between  the  inside 
surface  of  the  engine  cylinder  and  the  piston  during  the 
relatively  long  time  required  for  a  slow  speed  stroke.  An- 
other reason  is  that  the  heat  developed  by  the  compression 
of  the  explosive  mixture  is  largely  lost  (dissipated)  at  slow 
speed  of  starting.  The  result  is  that  only  the  most  easily 
evaporated  part  of  the  gasoline  can  be  vaporized  at  the  time 
of  starting  an  engine,  and  this  easily  vaporized  'part  is  only 
a  small  percentage  of  that  discharged  from  the  spray  nozzle 
of  the  carbureter.  It  is,  therefore,  necessary  to  take  a  large 
quantity  of  gasoline  into  the  engine  cylinders  to  secure  enough 
of  the  easily  vaporized  kind  to  start  combustion.  One  way 
to  obtain  an  explosive  mixture  very  rich  in  gasoline  is  to 
depress  the  float  rod  R  (Fig.  60)  by  hand,  so  that  a  small 
quantity  of  gasoline  will  overflow  from  the  spray  nozzle  into 
the  air  passage  A.  Gasoline  exposed  in  this  way  in  the  air 
passage  will  be  readily  vaporized  and  mixed  with  the  entering 
air  so  that  the  engine  will  receive  a  "rich"  explosive  mixture 
at  the  slow  speed  of  starting,  whether  the  engine  is  turned 
by  hand  or  by  an  electrical  or  mechanical  starting  device. 


70  GASOLINE  AUTOMOBILES 

Somewhat  different  devices  for  priming  carbureters  will  be 
explained  in  the  descriptions  of  other  carbureters. 

It  is  dangerous  to  let  very  much  gasoline  discharge  from 
the  spray  nozzle  of  a  carbureter  by  priming  when  the  engine 
is  very  cold,  because  under  these  conditions,  a  slow-burning 
ignition  flame  sometimes  comes  back  through  the  intake  valves 
into  the  carbureter,  and  if  a  puddle  of  gasoline  has  accumu- 
lated, there  is  danger  of  having  a  troublesome  fire.  There 
is  the  same  danger  of  a  fire*  in  the  carbureter  if  the  engine 
is  turned  over  a  number  of  times  without  getting  an  explosion 
in  the  cylinders  either  because  the  electric  switch  for  ignition 
has  not  been  turned  or  because  the  ignition  device  is  defective. 
Every  revolution  of  the  engine  pumps  more  gasoline  into 
the  cylinders  and  this  gasoline  is  left  condensed  on  the  pistons 
and  on  the  tops  of  the  cylinders.  The  engine  will  probably 
start  when  the  trouble  with  the  ignition  has  been  corrected 
and  the  accumulation  of  gasoline  has  evaporated.  Sometimes 
when  a  cold  engine  is  to  be  started  and  the  usual  methods 
of  priming  the  carbureter  are  ineffective,  a  teaspoonful  of 
gasoline  put  into  each  of  the  engine  cylinders  will  serve  to 
start  the  engine.  "When  the  engine  does  not  start  after  this 
"treatment"  there  is  probably  some  defect  in  the  ignition. 
If,  however,  too  much  gasoline  is  put  into  the  cylinders  for 
priming,  the  mixture  will  be  too  rich  for  engine  operation. 
The  need  is  then  for  more  air  rather  than  more  gasoline. 

Regulated  Nozzle  Carbureters.  The  carbureter  shown  in 
Fig.  60  has  the  float  valve  rigidly  attached  to  the  float  so 
that  when  the  float  is  raised,  the  valve  will  be  raised  an 
equal  amount.  Another  arrangement  of  the  float  and  valve 
is  shown  in  Fig.  61  in  which  the  float  valve  FV  is  at  the 
side  of  the  float  F,  which  is  made  of  cork  and  is  in  the  shape 
of  a  horseshoe.  The  short  lever  L  is  fastened  on  one  side 
to  the  top  of  the  float  and  at  the  other  end  is  forked  to  fit 

•Water  should  not  be  poured  on  a  gasoline  fire.  It  is  best  to  use 
the  spray  of  chemicals  from  a  good  kind  of  fire  extinguisher.  Such  a 
fire  can  be  smothered  by  throwing  blankets,  sand,  or  dirt  over  the 


GASOLINE  CARBURETERS  71 

around  the  rod  or  stem  attached  to  the  float  valve  FV.  This 
lever  is  supported  on  a  horizontal  pin  at  /.  When  the  left- 
hand  end  of  the  lever  is  pressed  downward  by  the  weight 
of  the  float  (when  the  gasoline  level  falls)  the  other  end  of 
the  lever,  which  is  attached  to  the  float  valve  FV  is  raised 
and  permits  gasoline  from  the  supply  pipe  G  to  flow  into  the 
float  chamber  C. 

The  carbureter  shown  in  Fig.  61  has  a  mechanical  means 
for  regulating  the  flow  of  gasoline  through  the  spray  nozzle. 
The  spray  nozzle  N  extends  into  the  middle  of  the  mixing 


To  Engine 

Cylinder 


FIG.  61.  —  Regulated  Nozzle  Carbureter. 

chamber  M  so  that  it  is  near  the  center  of  the  float  chamber. 
This  arrangement  has  the  advantage  that  the  flow  of  gasoline 
through  the  nozzle  is  not  much  affected  by  either  endwise  or 
sidewise  tilting.  The  needle  valve  or  pointed  stem  P  in  the 
opening  in  the  spray  nozzle  N  is  used  to  regulate  the  amount 
of  the  gasoline  going  into  the  mixing  chamber.*  The  main 


*  Sometimes  the  needle  valve  or  pointed  stem  is  at  such  an  angle  that 
by  lengthening  the  stem  it  can  be  extended  to  reach  to  the  dash  board 
or  instrument  board.  It  may  then  be  fitted  with  a  handle  intended  to 
be  turned  slightly  when  starting  the  engine,  in  order  to  get  a  mixture 
of  gasoline  and  air  suited  to  the  speed  of  the  engine. 


72  GASOLINE  AUTOMOBILES 

air  supply  enters  through  the  holes  shown  in  the  bottom  of 
the  carbureter  and  goes  into  the  air  passage  A  and  then 
past  the  spray  nozzle  into  the  mixing  chamber  M.  The 
amount  of  opening  of  the  auxiliary  air  valve  A V  is  propor- 
tional to  the  engine  speed.  The  auxiliary  air  current  has  the 
effect  at  high  engine  speeds — mainly  by  reducing  the  suction — 
of  checking  the  flow  of  gasoline  from  the  spray  nozzle.  The 
butterfly  throttle  valve,  as  shown  to  the  left  of  M,  regulates  the 
quantity  of  the  mixture  of  gasoline  and  air  going  to  the  engine 
cylinders.  A  throttle  valve  of  this  kind  is  simply  a  small 
damper  similar  to  those  in  the  smoke  pipes  of  furnaces  and 
stoves.  It  is  connected  to  the  throttle  lever  on  the  steering 
column  and  also  to  the  foot  pedal  called  the  accelerator.  Mov- 
ing the  throttle  lever  by  hand  or  depressing  the  accelerator 
with  the  foot  opens  this  valve  and  allows  more  explosive 
mixture  to  enter  the  engine  cylinders.  The  throttle  valve 
thus  regulates  the  speed  of  the  engine. 

Symbols  for  Carbureters.  In  the  following  descriptions 
of  carbureters  the  symbols  given  below  will  be  used  to 
designate  the  important  parts.  Keeping  these  in  mind,  it 
should  be  possible  to  understand  the  operation  of  any  car- 
bureter marked  with  these  symbols  by  casual  examination 
of  the  figures  going  with  the  description.  The  following 
symbols  are  used  to  mark  the  figures  in  this  chapter: 

A  Air  Intake. 

AA  Auxiliary  Air  Intake,  if  without  auxiliary  air  valve. 

AN  Auxiliary  Gasoline  Nozzle. 

AV  Auxiliary  Air  Valve    (for  high  speed  adjustment). 

C  Gasoline  Chamber  (also  called  float  chamber). 

D  Dash  Pot  (to  steady  valve  action). 

E  Exhaust  Gas  Connection. 

F  Float  in  Gasoline  Chamber. 

FV  Float  Valve. 

G  Gasoline  Supply  Pipe. 

J  Gasoline  Pool  or  "Puddle." 

L  Lever  on  Throttle  Valve  T. 

M  Mixing  Chamber. 

N  Gasoline  Spray  Nozzle. 


GASOLINE  CARBURETERS  73 

P  Needle  Valve  (also  called  pointed  stem). 

8  Valve  Seat. 

T  Throttle  Valve   (also  called  butterfly  valve). 

V  Air  Valve  (also  called  choke  valve). 

W  Weight  on  Weighted  Valve. 

X  Coil  Spring. 

Z  Expanding  Mixing   Tube    ("Venturi"). 

Weighted  Air  Valve  Carbureters.    A  somewhat  different 
type  of  carbureter  shown  in  Fig.  62,  similar  to  the  Kingston 


Air 


To  Engine  Intake 


FV 


FIG.  02. — Kingston  Carbureter. 

make,  is  used  on  some  Ford  automobiles.  The  gasoline 
enters  from  the  supply  pipe  G  into  the  float  chamber  when 
the  float  valve  FV  is  open.  The  opening  and  closing  of  the 
float  valve  are  regulated  by  the  cork  float  F  which  is  sup- 
ported on  a  horizontal  pin  at  /.  The  mixing  chamber  is  the 
unique  part  of  this  carbureter  and  is  so  designed  that  all 
air  entering  through  the  main  air  intake  A  must  pass  over 
a  little  pool  of  gasoline  in  a  sort  of  pit  /  in  the  bottom  of 
the  mixing  chamber.  The  amount  of  gasoline  supplied  is 


74  GASOLINE  AUTOMOBILES 

regulated  by  the  position  of  the  needle  valve  or  pointed 
stein  P  which,  by  adjusting  the  size  of  the  opening  in  the 
submerged  nozzle  at  0  controls  the  level  of  gasoline  in  the 
pool.  Obviously,  more  gasoline  will  be  taken  up  by  the  air 
when  the  level  is  high  than  when  low.  On  account  of  having 
such  a  gasoline  pool,  this  kind  of  carbureter  is  sometimes 
called  a  "puddle"  type.  At  low  engine  speeds  the  suction 
is  not  great  enough  to  raise  the  air  valve  AV  as  it  is  held 
down  with  the  weights  W,  W;  and  all  the  air  for  the  explo- 
sive mixture  together  with  the  gasoline  vapor  it  picks  up 
in  the  gasoline  pool  must  go  up  through  the  tube  U,  and 
a  very  "rich"  mixture  is  thus  obtained  for  starting  and  for 
running  at  low  engine  speeds.  With  increasing  speeds  the 
weighted  air  valve  AV  opens  more  and  more  so  that  at  about 
the  highest  engine  speed,  it  is  wide  open,  and  gives  a  much 
diluted  explosive  mixture.  The  amount  of  gasoline  and  air 
mixture  entering  the  engine  intake  pipe  is  controlled  in  the 
usual  manner  by  a  butterfly  throttle  valve  T.  At  low  engine 
.speeds,  as  when  starting,  the  air  cannot  fail  to  take  up  the 
gasoline  vapor  no  matter  how  low  the  velocity  of  air  passing 
over  the  surface  of  the  gasoline  pool.  The  only  adjustment 
on  this  carbureter  is  by  means  of  the  needle  valve  P.  A  very 
rich  mixture  for  starting  in  cold  weather  is  secured  by  partly 
closing  the  air  valve  or  choke  damper  V  in  the  main  air 
passage. 

The  carbureter  shown  in  Fig.  63  has  no  essential  parts 
different  from  those  already  described,  except  as  to  the  kind 
of  auxiliary  air  valve.  The  main  air  opening  is  through  the 
nir  bend  A  at  the  bottom  of  the  carbureter.  The  mixing 
chamber  M  is  at  the  top  of  the  spray  nozzle  N  which  is  flared 
out  into  a  conical  shape.  There  is  an  overhead  needle  valve 
or  pointed  stem  P  which  extends  into  the  top  of  the  spray 
nozzle  and  is  to  be  used  for  regulating  the  amount  of  gasoline 
used.  The  supply  of  auxiliary  air  is  controlled  by  a  series 
of  metal  balls  E,  B,  set  into  tightly  fitted  seats  8  in  a  circular 
plate  near  the  top  of  the  carbureter,  just  under  the  cover 
plate.  At  high  speeds,  the  engine  suction  raises  these  balls 


GASOLINE  CARBURETERS 


75 


from  their  seats  and  air  is  admitted  through  the  openings 
thus  uncovered. 

Marvel  Carbureter.  The  carbureter  shown  in  Fig.  64 
is  provided  with  two  nozzles.  One  nozzle  N  is  controlled 
by  the  needle  valve  P.  At  low  speeds  the  air  from  the  air 
passage  A  passes  into  the  tube  surrounding  the  nozzle  N  from 
which  it  takes  up  the  sprayed  gasoline  vapor.  At  high  speeds, 
however,  the  air  goes  in  two  different  directions  (1)  through 


L-, 


FIG.  63. — Kingston  Carbureter  with  Balls  for  Auxiliary  Air  Valves. 

the  tube  around  the  nozzle  N,  and  (2)  through  the  flat 
damper  shaped  auxiliary  air  valve  AV  which  at  low  speeds 
is  kept  closed  by  a  spiral  spring  X.  There  is  an  auxiliary 
or  high  speed  gasoline  nozzle  AN  placed  close  to  the  auxiliary 
air  valve  so  that  when  this  valve  opens  the  air  velocity  will 
be  high  enough  around  this  auxiliary  gasoline  nozzle  to  take 
up  more  gasoline.  The  air  valve  or  choke  damper  in  the  air 
passage  A  is  provided  so  that  it  can  be  closed  when  the  engine 
is  to  be  started,  in  order  to  give  a  rich  mixture.  The  car- 
bureter has  a  jacket  similar  to  the  water  jackets  on  engine 


76 


GASOLINE  AUTOMOBILES 


cylinders  in  which  hot  exhaust  gas  from  the  engine  exhaust 
pipe  circulates.  A  damper  in  the  pipe  carrying  the  exhaust 
gas  to  the  jacket  when  opened,  allows  some  of  the  hot  exhaust 
gas  from  the  engine  exhaust  pipe  to  flow  through  cored  pas- 
sages E  shown  in  the  figure.  The  heat  from  the  hot  gas 
is  for  making  vaporization  in  the  carbureter  more  rapid  in 
cold  weather.  The  damper  regulating  the  flow  of  this  hot 


FV- 


Air 


FlG.  64.— Marvel  Carbureter. 

exhaust  gas  is  controlled  automatically  by  the  lever  L  on  the 
throttle  valve  T  in  such  a  way  that  when  the  throttle  valve 
is  opened  half  way  or  more  the  exhaust  gas  damper  is  closed. 
"Plain  Tube"  Carbureter.  Fig.  65  shows  the  parts  of 
a  very  common  type  of  carbureter.  The  gasoline  from  the 
float  chamber  is  regulated  in  its  flow  by  the  high  speed 
adjustment  needle  1  from  which  the  gasoline  flows  into  the 
pool  below  the  valve  3  or  into  the  long  "idling"  tube  con- 
trolled by  the  valve  2,  both  of  which  are  in  communication 


GASOLINE  CARBURETERS 


77 


with  the  air  bleeder  valve  3  where  the  gasoline  level  is  main- 
tained the  same  as  in  the  float  chamber.  The  air  bleeder 
valve  3  admits  a  little  air  into  the  gasoline  passages  for  the 
purpose  of  breaking  up  the  gasoline  into  a  mist  as  it  dis- 
charges from  the  expanding  tube  Z  into  the  mixing  chamber 
M.  By  the  use  of  this  small  amount  of  air  complete  vaporiza- 
tion in  the  mixing  chamber  is  made  much  easier.  The  gaso- 
line pool  and  the  passages  just  above  it  are  intended  to  fur- 
nish the  extra  amount  of  gasoline  needed  when  the  throttle 
valve  is  suddenly  opened.  (Fig.  66.)  The  "idling"  tube  con- 
trolled by  valve  2  is  in  the  center  of  the  main  gasoline  supply 


FlG.  65. — Stromberg  "Plain 

Tube ' '  Carbureter.     Throttle 

Valve  Nearly  Closed. 


FlG.  66. — Stromberg  "Plain 

Tube"  Carbureter.     Throttle 

Valve  Wide  Open. 


passage  and  is  intended  to  supply  a  small  amount  of  gasoline 
to  the  engine  when  the  throttle  valve  is  nearly  closed ;  as,  for 
example,  when  the  automobile  is  standing  and  the  engine  is 
running  or  when  starting  the  engine.  (Fig.  65.)  In  the  oper- 
ation of  this  "idling"  tube  some  air  is  drawn  through  a 
restricted  opening  under  the  control  of  the  adjustment  valve  2. 
This  air  mixes  with  the  gasoline  and  discharges  it  as  a  spray 
through  the  small  nozzle  just  above  this  adjustment  needle. 
When  the  throttle  valve  is  more  than  half  way  open  there  is 
insufficient  suction  to  discharge  gasoline  spray  through  the 
"idling"  nozzle  and  all  the  gasoline  spray  comes  from  the 
holes  opening  into  the  expanding  tube  Z. 


78 


GASOLINE  AUTOMOBILES 


A  detail  showing  the  operation  of  the  air  bleeder  valve  3, 
and  of  the  small  gasoline  tubes  discharging  into  the  expand- 
ing nozzle  Z  is  shown  in  Fig.  67. 


Fie.  67. — Stromberg  Air  Bleeder  Valve. 

A  somewhat  simpler  type  of  the  same  make  of  carbureter 
is  shown  in  Fig.  68  which  has  two  nozzles  for  the  gasoline 


Air 


FIG.  68. — Stromberg  Double  Nozzle  Carbureter. 


supply.  At  low  speed  the  nozzle  N  discharges  gasoline  vapor 
into  the  expanding  tube.  At  high  speed  the  additional  air 
supply  needed  comes  through  the  auxiliary  air  valve  AV 


GASOLINE  CARBURETERS  79 

which  regulates  also  automatically  a  gasoline  supply  through 
the  auxiliary  nozzle  AN.  This  gasoline  discharges  in  the 
direction  of  the  air  flowing  through  the  auxiliary  air  valve 
AV.  By  this  method  there  is  an  extra  supply  of  gasoline  for 
high  speed  and  for  heavy  pulling.  This  carbureter  has  an  air 
valve  or  choke  damper  V  in  the  air  inlet  for  starting  the 
engine  in  cold  weather.  There  is  a  connection  from  this  choke 
air  valve  to  the  auxiliary  air  valve  AV,  so  that  closing  the 
choke  valve  closes  tightly  the  auxiliary  valve. 

The  choke  air  valve  is  controlled  either  from  the  dash  or 
from  the  steering  column,  depending  on  the  method  of  in- 
stallation. 

Stewart  Carbureter.  The  unique  feature  of  the  car- 
bureter shown  in  Fig.  69  is  that  it  has  a  relatively  heavy 
air  valve  W  surrounding  the  spray  nozzle  N.  This  cap- 
like  air  valve  W  rests  on  its  seat  S  and  shuts  off  any  air 
flowing  from  the  air  chamber  marked  "Air."  As  soon  as 
the  engine  starts,  vacuum  is  formed  in  the  mixing  chamber 
M  and  the  valve  W  is  lifted  from  its  seat  in  proportion  to  the 
amount  of  the  engine  suction.  At  the  same  time  because  of 
this  suction,  the  gasoline  will  be  sucked  up  through  the  spray 
nozzle  N.  The  lower  end  of  the  air  valve  W  extends  down 
and  is  surrounded  by  the  gasoline  in  the  extension  of  the  float 
chamber,  and  the  extreme  lower  end  has  a  needle  valve  (some- 
times called  a  metering  pin)  P  for  a  central  guide.  The 
needle  valve  extends  upward  into  the  central  tube  in  the 
valve  W,  so  that  as  the  suction  varies,  the  position  of  the 
air  valve  W  will  move  up  and  down  to  regulate  the  flow 
of  air  by  the  distance  it  rises  above  the  seat  8,  and,  the 
amount  of  gasoline  by  the  distance  the  central  tube  in  the 
valve  is  above  the  metering  pin  P.  This  device  is  intended 
to  regulate  the  volume  of  air  and  the  amount  of  gasoline 
going  into  the  mixing  chamber  so  as  to  increase  or  decrease 
the  amount  of  each  in  the  same  proportion.  Most  of  the  air 
going  through  the  carbureter  passes  through  the  space  be- 
tween the  air  valve  and  its  seat  8,  but  the  small  amount  of 
air  necessary  for  starting  the  engine  is  drawn  through  the 


80 


GASOLINE  AUTOMOBILES 


very  small  air  passages  0  in  a  circuitous  path  to  discharge 
around  the  spray  nozzle  N.  To  prevent  vibration  or  chatter- 
ing of  the  air  valve  W,-  its  lower  end  fits  loosely  in  a  dash- 
pot  D.  There  is  a  restricted  flow  of  gasoline  from  the  ex- 
tended float  chamber  through  the  ball  valves  B  into  the  dash- 


FIG.  69.— Stewart  Carbureter. 

pot  so  that  the  rapid  movement  of  the  air  valve  W  is  pre- 
vented. The  only  adjustment  of  this  carbureter  is  by 
raising  or  lowering  the  needle  valve  P  and  thereby  increas- 
ing or  decreasing  the  amount  of  gasoline  going  into  the 
mixing  chamber  M. 

HoUey  Carbureter.    Fig.  70  shows  a  type  of  carbureter 


GASOLINE  CARBURETERS 


81 


which  differs  in  many  details  from  those  already  described. 
The  main  air  supply  enters  through  the  passage  A  at  the  side 
of  the  carbureter  and  after  passing  around  the  bottom  of 
the  large  central  tube  enters  the  mixing  chamber  M.  The 
gasoline  enters  from  the  pipe  G  and  when  the  float  valve  FV 
is  opened,  passes  into  the  float  chamber  C.  The  float  valve 
is  controlled  by  the  circular  cork  float  F  supported  on  a 
horizontal  pin  /.  The  flow  of  gasoline  is  through  the  hole  Y 
into  the  space  around  the  needle  valve  P  and  then  upward 
into  the  cup  J  through  the  spray  nozzle  N.  When  the  engine 


G 


FIG.  70. — Holley  Carbureter. 

is  not  running,  the  float  regulates  the  level  in  the  pool  cup  J 
so  that  the  gasoline  fills  it  sufficiently  to  nearly  submerge 
the  lower  end  of  the  small  tube  or  auxiliary  gasoline  nozzle 
AN.  When  starting  the  engine  the  butterfly  throttle  valve 
T  is  nearly  closed  and  the  explosive  mixture  of  gasoline  and 
air  is  drawn  through  the  tube  AN  with  high  velocity  as  there 
is  then  a  very  high  suction,  giving  a  mixture  rich  in  gaso- 
line. The  tube  AN  continues  to  supply  the  engine  at  small 
throttle  openings,  that  is,  at  low  speeds,  but  as  the  throttle 
valve  is  opened  more  and  more  with  increased  speed  the 
level  in  the  gasoline  pool  J  gradually  sinks  so  that  at  moder- 


82 


GASOLINE  AUTOMOBILES 


ate  and  high  speeds  all  the  mixture  is  supplied  through  the 
main  mixing  tube  M.  A  slight  modification  is  shown  in 
Fig.  71  which  is  intended  for  attachment  to  a  horizontal 
intake  pipe  of  an  engine.  In  this  case  the  auxiliary  tube 
AN  is  bent  so  as  to  be  horizontal  and  discharges  close  to  the 
throttle  valve  T.  Some  carbureters  of  this  type  have  an 
auxiliary  air  passage  A  A  (Fig.  70)  which  is  always  open. 
It  gives  a  very  direct  flow  of  air  for  starting. 

The  Schebler  Model  L  Carbureter  as  shown  in  Fig.  72 
has  a  device  for  regulating  the  nozzle  opening  by  means  of 
the  needle  valve  or  metering  pin  P  which  is  operated  auto- 


Air 


FIG.  71. — Holley  Carbureter  for  Horizontal  Intake  Pipe. 

matically  with  the  movement  of  the  butterfly  throttle  valve  T. 
The  flow  of  gasoline  through  the  nozzle  can  be  adjusted  in 
this  type  of  carbureter  for  an  intermediate  speed  in  addition 
to  the  usual  low  and  high  speed  adjustments  as  in  most  other 
types.  Each  of  these  three  adjustments  is  independent  of 
the  others.  The  opening  of  the  butterfly  throttle  valve  T 
for  high  speed  or  a  heavy  pull  raises  the  metering  pin  (needle 
valve)  P  and  increases  the  supply  of  gasoline.  The  auxiliary 
air  valve  AV  is  shown  at  the  left-hand  side  of  the  figure. 
A  priming  pin  and  lever  are  shown  just  above  the  cork  float 
F.  By  pressing  on  this  pin  the  level  of  gasoline  in  the  float 
chamber  and  in  the  nozzle  is  raised  to  provide  a  very  rich 


GASOLINE  CARBURETERS 


83 


mixture  for  starting.  This  type  of  carbureter  must  be  pro- 
vided with  a  warm  air  connection  as  shown  in  Fig.  73.  The 
air  taken  into  the  main  air  opening  goes  through  this  special 


Air 
FIG.  72.— Schebler  Model  L  Carbureter. 

fitting  which  is  attached  to  the  engine  exhaust  pipe  and  has 
suitable  slots  around  the  pipe  for  the  admission  of  air. 

A  dash-control  (Fig.  74)  is  also  shown  for  the  auxiliary 


FiG.  73. — Hot  Air  or  "Stove"  Connection. 

air  valve  spring,  which  is  adjusted  by  a  lever  arranged  to 
be  moved  by  a  handle  on  the  instrument  board  of  the  auto- 
mobile. When  the  handle  is  in  the  position  marked  "gas" 


84  GASOLINE  AUTOMOBILES 

the  setting  is  for  a  rich  mixture.  As  the  engine  warms  up 
after  running  a  few  minutes,  the  handle  should  gradually 
be  moved  back  toward  the  "air"  position  to  obtain  the  best 
running  conditions. 

As  this  carbureter  is  somewhat  more  complicated  than 
most  others;  a  brief  explanation  of  its  adjustment  will  be 
given.  It  is  poor  policy,  however,  to  experiment  with  cur- 
bureter  adjustments  either  for  practice  in  making  adjust- 
ments, or  for  experimentation.  An  experienced  automobile 
mechanic  who  is  accustomed  to  one  type  of  engine  or  car- 
bureter, can  usually  get  much  better  results  from  carbureter 
adjustment  by  "sound"  than  a  person  inexperienced  with 
practical  automobile  work  can  expect  to  get  no  matter  how 


TO  CARBURETER 

FIG.  74. — Dash  Control  Lever. 

much  theoretical  education  he  may  have.  The  method  of 
adjustment  of  this  carbureter  is  to  regulate,  first  the  spring 
on  the  auxiliary  air  valve  so  that  it  rests  lightly  but  firmly 
on  its  seat. 

The  needle  valve  P  should  be  closed  by  turning  the  adjust- 
ment screw  toward  the  right.  It  is  then  turned  to  the  left 
about  four  or  five  turns  and  the  carbureter  primed  or  flushed 
by  pulling  up  the  priming  lever  and  holding  it  up  for  about 
five  seconds.  Now  open  the  throttle  valve  about  one-third  and 
start  the  engine.  After  closing  the  throttle  slightly,  the  throt- 
tle lever  screw  and  the  needle  valve  adjusting  screw  are 
regulated  so  that  the  engine  runs  with  even  explosions  at 
the  desired  speed.  This  is  the  low-speed  adjustment. 

After  getting  a  good  adjustment  with  the  engine  running, 
the  needle  valve  P  should  not  be  changed  again.  The  inter- 


GASOLINE  CARBURETERS  85 

mediate  and  high-speed  adjustments  are  made  on  the  dials. 
The  pointer  on  the  right  or  intermediate  speed  dial  should 
be  set  halfway  between  figures  1  and  3.  The  spark  ignition 
should  be  set  for  moderate  speed  and  the  throttle  opened  so 
that  the  roller  on  the  track  running  below  the  dials  is  in 
line  with  the  first  dial.  If  the  engine  back-fires,  with  the 
throttle  in  this  position,  the  indicator  or  pointer  should  be 
turned  a  little  more  toward  figure  3 ;  if  the  mixture  is  too 
rich,  the  indicator  should  be  turned  back,  or  toward  figure  1, 
until  the  engine  is  running  properly  with  the  throttle  in 
intermediate  speed  position.  For  high-speed  adjustment  the 
throttle  is  opened  wide  and  the  adjustment  made  for  high 
speed  on  the  second  dial  in  the  same  manner  as  the  adjust- 
ment for  intermediate  speed  on  the  first  dial. 

Rayfield  Model  G  Carbureter.  A  somewhat  complicated 
carbureter  illustrated  in  Fig.  75  has  two  gasoline  nozzles 
and  two  air  inlets,  both  of  which  are  used  for  the  admission 
of  auxiliary  air.  There  are  no  air  valve  adjustments  but  two 
gasoline  adjustments,  one  for  low  speed  and  the  other  for 
high  speed.  For  low-speed  operation  air  is  taken  into  the 
mixing  chamber  through  the  main  or  "constant"  opening 
A.  In  the  mixing  chamber  M  this  air  mixes  with  the  gaso- 
line vapor  which  the  engine  suction  draws  from  the  nozzle 
below  the  valve  Pj.  When  the  speed  increases,  the  engine  suc- 
tion opens  the  upper  automatic  (auxiliary)  air  valve  AV 
and  increases  the  amount  of  air.  In  the  automatic  movement 
of  this  air  valve  it  presses  down  on  the  metering  pin  P2  just 
below  so  that  at  the  same  time  additional  "gasoline  comes 
through  this  auxiliary  nozzle.  A  second  auxiliary  air  valve 
at  the  bottom  of  the  carbureter  opens  and  closes  with  the 
main  or  upper  automatic  air  valve  AV  as  they  are  con- 
nected together  by  levers  and  links.  The  effect  of  the 
lower  auxiliary  air  valve  is  to  give  a  still  greater  volume 
of  air  at  high  engine  speeds.  The  upper  automatic  air  valve 
is  controlled  by  the  tension  of  a  spiral  spring  shown  directly 
below  it  in  the  figure.  A  small  vertical  rod  connects  this 
valve  to  a  dashpot  filled  with  gasoline  on  its  lower  side.  This 


86 


GASOLINE  AUTOMOBILES 


dashpot  is  provided  for  the  purpose  of  preventing  vibration 
of  the  valve  and  has  also  the  effect  of  forcing  out  the  gasoline 
from  the  auxiliary  valve  P2  when  the  throttle  valve  is  sud- 
denly opened,  and  a  quick  response  of  the  engine  is  desired 
in  the  amount  of  power  to  be  delivered. 

This  carbureter  is  heated  by  the  circulation  through  its 
jacket  of  ~kot  water  which  is  taken  from  a  pipe  attached 
to  the  upper  part  of  the  water  jacket  on  the  engine  where 
the  temperature  of  the  engine  cooling  water  is  highest.  This 
water  is  discharged  from  the  carbureter  jacket  through  a  pipe 


AV 


— -M/r 

FIG.   75.— Eayfield   Carbureter. 

connected  usually  to  the  suction  side  of  the  cooling  water 
pump.  These  pipe  connections  provide  a  constant  circulation 
of  hot  water  through  the  jackets  of  the  carbureter.  The  main 
or  ''constant"  air  opening  A  is  connected  by  a  piece  of 
flexible  tubing  to  the  usual  attachment  (Fig.  73)  on  the  ex- 
haust pipe  for  heating  the  air.  A  dash-control  wire  is  con- 
nected to  the  valve  Pl  in  such  a  way  that  its  movement  opens 
or  closes  the  main  gasoline  nozzle. 

The  vertical  tube  at  the  left  of  the  mixing  chamber  M 
discharges  a  rich  mixture  of  gasoline  vapor  and  air  above 
the  throttle  valve  for  idling. 


GASOLINE  CARBURETERS 


87 


Compound  Nozzle  Carbureter.  In  another  type  of  car- 
bureter the  gasoline  is  supplied  from  a  Compound  nozzle 
which  has  actually  two  nozzles,  one  inside  the  other  as 
illustrated  in  Figs.  76  and  77.  It  will  be  noted  that  when 
the  throttle  valve  is  closed  (Fig.  76)  the  outside  nozzle  is 
supplied  by  a  gravity  flow  by  the  constant  level  maintained 
in  the  auxiliary  fuel  well  W.  This  compound  nozzle  is  satis- 
factory for  giving  a  uniform  explosive  mixture  of  gasoline 
and  air  for  varying  suction  in  the  engine  cylinders.  Other 
carbureters  have  been  made  to  use  practically  the  same  prin- 
ciple by  combining  the  two  nozzles  of  this  compound  type 
in  a  single  one,  and  have  provision  for  suitable  air  bleeds 


FIG.  76. — Compound  Nozzle 
(Throttle  Valve  Closed). 


FIG.  77. — Compound  Nozzle 
(Throttle  Valve  Open). 


(Fig.  67)  so  that  the  amount  of  gasoline  will  be  more  and 
more  weakened  by  excess  air  as  the  suction  increases. 

Zenith  Carbureter.  The  carbureter  shown  in  Fig.  78 
differs  from  most  of  the  carbureters  which  ^have  been  ex- 
plained in  that  it  has  no  auxiliary  air  valve.  It  has  a  com- 
pound nozzle  (Figs.  77  and  78)  consisting  of  an  inner  nozzle 
for  which  the  gasoline  is  supplied  direct  from  the  float  chamber 
C,  and  an  outer  nozzle  for  the  purpose  of  reducing  the  strength 
of  the  mixture  at  high  speeds.  This  provision  as  to  the 
gasoline  supply  is  possible  because  the  amount  of  gasoline 
passing  through  the  outside  or  compensating  nozzle  is  constant 
at  all  speeds.  When  the  speed  of  the  engine  increases  the 
amount  of  air  drawn  in  through  the  air  passage  A  increases 


88  GASOLINE  AUTOMOBILES 

in  proportion  and  makes  the  compensating  mixture  relatively 
weak.  This  device  has,  therefore,  the  same  effect  as  the 
auxiliary  air  valve  on  other  types. 

The  Zenith  carbureter  has  special  provision  for  starting 
and  idling  without  a  load.  There  is  a  specially  constructed 
gasoline  tube  extending  from  below  the  compound  nozzle  to 
near  the  top  of  the  left-hand  carbureter  wall.  The  outlet  of 
this  side'  tube  is  in  a  so-called  priming  hole  SN  at  the  edge 
of  the  throttle  valve  T,  where  obviously  the  suction  is  greatest 


FIG.  78. — Zenith  Carbureter. 

when  the  valve  is  nearly  closed.  The  gasoline  is  drawn  up 
by  the  suction  of  the  engine  to  discharge  from  the  priming 
hole  where  it  mixes  with  a  small  amount  of  air  passing  through 
the  throttle  valve  so  as  to  give  a  rich  explosive  mixture  for 
starting  the  engine.  The  richness  of  this  starting  mixture 
can  be  regulated  by  adjusting  the  regulating  screw  shown 
in  the  figure  near  the  top  of  the  side  passage.  This  regulating 
screw  admits  a  small  amount  of  air  to  the  priming  hole.  At 
high  speeds  when  the  throttle  valve  is  wide  open,  the  priming 
hole  ceases  to  discharge,  and  the  compound  nozzle  is  sufficient 
to  adjust  the  mixture  for  any  intermediate  engine  speed. 


GASOLINE  CARBURETERS  89 

Tillotson  Carbureter.  The  carbureter  shown  in  Fig.  79 
has  a  unique  method  of  regulating  the  air  supply.  The  only 
regulation  is  by  means  of  the  gasoline  needle  valve  P.  The 
air  comes  through  the  air  opening  at  the  top  and  is  drawn 
through  the  V-shaped  passage  formed  by  steel  reeds  R.  At  low 
engine  speeds  the  reeds  bear  on  both  sides  against  the  main 
gasoline  nozzle  N  (Fig.  80)  ;  but  as  the  engine  speed  and  the 
suction  increase,  the  reeds  are  spread  apart  and  make  a  larger 
opening  for  the  passage  of  air.  A  small  air  supply  to  assist 


. — Tillotson  Carbureter. 


FIG.  80. — Eeeds  of  Tillotson 
Carbureter. 


in  vaporizing  the  gasoline  enters  through  the  air  holes  A  A  at 
the  bottom  of  the  needle  valve  P. 

An  auxiliary  gasoline  nozzle  AN  extends  upward  from  the 
float  chamber  and  at  high  engine  speed,  the  engine  suction 
draws  an  additional  gasoline  supply  from  this  nozzle. 

Johnson  Carbureter.  Another  type  of  carbureter  which 
is  somewhat  similar  to  the  Stewart  type  described  on  page  79 
is  shown  in  Fig.  81.  The  similarity  is  in  the  application  of 
a  weighted  air  valve  V.  The  outside  of  the  valve  V  is  a  thin 
metal  tube  with  notches  in  its  lower  edge  which  allow  a  smell 
quantity  of  air  to  pass  into  the  mixing  tube  M  when  the 


90  GASOLINE  AUTOMOBILES 

engine  is  idling.  Gasoline  enters  the  float  chamber  through 
the  supply  pipe  and  discharges  as  a  spray  through  the  nozzle 
N.  The  gasoline  discharge  can  be  controlled  by  the  move- 
ment of  the  needle  valve  P.  When  the  air  valve  V  is  in  its 
lowest  position  there  will  be  very  little  flow  of  gasoline  vapor. 
As  soon  as  the  engine  suction  increases  the  valve  V  will  be 
lifted  and  there  will  be  a  flow -of  air  around  the  nozzle  and 
a  discharge  of  gasoline  vapor  from  the  nozzle  in  proportion 
to  the  amount  of  suction.  The  air  enters  the  carbureter  from 
the  side  through  the  passages  marked  A  and  goes  downward 


6aso!ine 


FIG.  81.— Johnson  Carbureter. 

to  the  lower  chamber  surrounding  the  nozzle  N  through  a 
series  of  holes  not  shown  in  the  figure.  As  the  throttle  valve 
T  is  opened  more  and  more,  the  cylindrical  valve  V  is  raised 
and  permits  the  entrance  of  additional  air  around  the  gaso- 
line spray  nozzle  N.  The  slots  at  the  base  of  the  cylindrical 
frame  are  intended  to  supply  only  enough  air  for  a  rich  mix- 
ture when  starting  the  engine.  The  ring-shaped  opening 
and  the  holes  connecting  the  annular  space  around  the  nozzle 
N  with  the  space  marked  A,  supply  enough  air  for  all  oper- 
ating conditions.  The  only  adjustment  of  the  carbureter  is 
by  means  of  the  needle  valve  P. 

The  weighted  valve  V  has  radial  blades  or  ribs  attached 


GASOLINE  CARBURETERS  91 

at  one  end  of  its  central  shaft  and  at  the  other  to  the  cylin- 
drical frame  of  the  valve.  The  explosive  mixture  discharging 
against  the  blades  of  valve  V  is  given  a  rotary  motion  by 
projections  (not  shown  in  the  figure)  on  the  expanding  tube 
(Venturi)  surrounding  the  lower  end  of  the  valve  V.  This 
rotary  motion  of  the  mixture,  gives  also  a  rotary  motion  to 
the  valve.  This  mixture  and  the  additional  air  entering 
through  the  ring-shaped  opening  are  mixed  by  this  motion, 
with  the  result  that  an  unusually  good  mixture  is  delivered 
to  the  engine.  It  is  difficult  to  test  the  rotary  operation  of 
a  valve  of  this  kind  so  as  to  know  whether  it  is  actually 
operating  as  intended.  Generally,  the  operation  of  such  de- 
vices is  good  when  new;  but  usually,  after  a  little  time,  they 
fail  to  operate. 

Schebler  Carbureter — Model  A.  Fig.  82  shows  a  some- 
what complicated  carbureter  of  the  plain  tube  type.  The  air 
enters  through  the  main  air  passage  A  and  passes  upward 
through  a  slightly  expanding  or  Venturi  tube  around  a  com- 
pound spray  nozzle  12.  The  gasoline  supply  enters  at  G 
through  the  float  valve  FV.  From  the  float  chamber  there 
are  two  paths  for  the  gasoline  to  discharge.  One  path  is 
around  the  "idling"  needle  valve  9  and  through  the  pas- 
sage 7.  The  other  path  is  around  the  main  gasoline  needle 
valve  10.  When  starting  the  engine,  especially  in  cold  weather, 
if  the  choke  valve  V  is  closed  the  air  supply  will  be  very  much 
restricted  and  there  will  be  a  strong  suction  to  draw  gasoline 
through  the  irregular  passage  7  to  discharge  through  the 
auxiliary  gasoline  nozzle  AN,  just  above  the  partly  closed  posi- 
tion of  the  throttle  valve  T.  With  the  throttle  valve  in  this 
position,  some  gasoline  will  also  be  drawn  from  three  holes 
marked  13  and  the  "lip"  marked  6.  This  gives  a  rich  mix- 
ture which  makes  starting  easy. 

When  the  engine  is  running  idle  and  the  throttle  valve  T 
is  nearly  closed  there  will  be  only  a  small  amount  of  air 
passing  through  the  expanding  tube  into  the  mixing  chamber 
M  and  its  velocity  will  not  be  sufficient  to  draw  gasoline 
from  the  holes  13  and  the  "lip"  6.  But  there  will  be  a 


92 


GASOLINE  AUTOMOBILES 


considerable  suction  in  the  passage  7  and  some  of  the  air 
entering  through  the  main  air  passage  will  pass  under  the 
edge  of  the  expanding  tube  and  through  the  passage  11  from 
which  it  will  discharge  to  mix  with  the  gasoline  from  the 
passage  7.  The  mixture  of  gasoline  and  air  thus  obtained 
will  be  discharged  from  the  auxiliary  nozzle  AN  just  above 
the  throttle  valve  T.  When  the  throttle  valve  is  opened 
more  and  more  the  engine  suction  will  draw  increasing 
amounts  of  air  through  the  expanding  tube  and  will  draw 
gasoline  vapor  through  the  holes  13  in  the  nozzle  12.  This 


1.    2, 


34  5  6     78J 
FIG.  82.— Schebler  Model  A  Carbureter. 

incoming  air  will  strike  the  projecting  "lip"  6  on  the  nozzle 
and  some  of  it  will  enter  the  hole  on  its  lower  side.  The 
pressure  of  this  air  will  force  down  the  gasoline  in  the  nozzle 
12  so  that  the  level  in  the  passage  connected  to  the  opening 
6  will  be  lowered  sufficiently  to  uncover  holes  between  this 
passage  and  the  passage  4.  When  these  holes  are  uncovered 
the  air  will  pass  through  them  and  mix  with  gasoline  in  the 
passage  4.  Because  of  this  combined  flow  of  gasoline  and  air 
through  the  passages  of  the  nozzle  there  will  be  a  discharge 
of  explosive  mixture  of  gasoline  and  air  from  the  holes  13 
into  the  mixing  chamber  M.  At  the  same  time  there  will 
be  some  discharge  from  the  idling  jet  or  auxiliary  gasoline 


GASOLINE  CARBURETERS  93 

nozzle  AN  until  the  throttle  valve  is  about  half  way  opened ; 
but  when  wide  open  the  flow  through  AN  ceases.  When  the 
throttle  valve  T  is  wide  open,  as  it  would  be  for  high  engine 
speed,  there  is  unrestricted  flow  of  air  through  the  expanding 
tube  and  also  a  maximum  amount  of  suction  at  the  holes  13 
in  the  nozzle.  This  large  flow  of  air  exerts  increased  pressure 
on  the  "lip"  6  causing  the  air  to  enter  still  farther  into  the 
passage  connected  to  the  opening  under  the  "lip"  and  lowers 
the  gasoline  level  by  the  same  amount  that  the  air  enters. 
This  permits  more  air  to  be  drawn  through  the  connecting 
holes  between  this  passage  and  the  passage  4.  Thus  the 
proportion  of  air  and  gasoline  delivered  to  the  mixing  cham- 
ber M  is  kept  constant  because  of  the  varying  amount  of  gaso- 
line discharged  from  the  holes  13. 

After  starting  and  warming  up  the  engine,  it  is  neces- 
sary to  close  the  choke  air  valve  V  until  the  parts  of  the 
engine  are  sufficiently  heated  to  give  good  air  temperature. 
An  engine  equipped  with  this  carbureter  will  start  readily 
with  the  choke  air  valve  closed  one-half  to  three-quarters  of 
the  way.  When  the  weather  is  very  cold  it  is  sometimes 
necessary  to  close  this  valve  entirely,  but  this  should  be  done 
only  for  an  instant  as  it  cuts  off  practically  all  the  air  and 
delivers  a  mixture  much  too  rich  in  gasoline  for  operating 
the  engine. 

Cadillac  Carbureter.  Several  novel  features  are  found 
on  the  Cadillac  carbureter,  Fig.  83.  The  gasoline  supply  is 
through  a  nozzle  N  placed  at  the  throat  of  an  expanding  or 
so-called  Venturi  tube  Z.  The  main  or  primary  air  supply 
is  taken  in  through  an  opening  on  the  side  of  the  carbureter 
as  shown.  The  auxiliary  air  valve  AV  is  a  shutter  type  which 
has  a  counter  weight.  This  valve  is  controlled  by  a  coil 
spring  X. 

A  throttle  pump  shown  in  the  figure  is  regulated  by 
the  movement  of  the  throttle  valve  T.  Its  purpose  is  to 
force  gasoline  through  the  spray  nozzle  N  when  the  throttle 
is  opened  suddenly  and  the  engine  speed  is  to  be  increased 
quickly.  When  the  throttle  is  opened  slowly,  the  throttle 


94  GASOLINE  AUTOMOBILES 

pump  has  little  or  no  effect  upon  the  flow  of  the  gasoline 
through  the  spray  nozzle. 

Packard  Carbureter.  This  carbureter  as  shown  at  the 
left-hand  side  of  Fig.  85,  page  99,  is  of  the  usual  auxiliary 
air  valve  type.  The  main  air  supply  at  the  left  of  the  *arbu- 
reter  furnishes  all  the  air  at  low  speeds.  This  air  current 
picks  up  the  gasoline  from  the  stand  pipe  nozzle  N.  "When 
the  engine  speed  and  the  suction  are  increased,  the  auxiliary 
air  valve  opens  and  supplies  the  additional  air  needed.  The 
opening  and  closing  of  this  valve  are  regulated  by  the  ten- 


CaM.BffSi'n, 
DrainPfpe] 

FIG.  83.— Cadillac  Carbureter. 

sion  on  its  two  springs,  one  inside  the  other.  This  tension 
is  adjusted  by  two  cams  under  the  springs.  Connections  to 
these  cams  are  made  to  the  control  board  on  the  dash  so 
that  the  adjustment  can  be  made  from  the  driver's  seat. 
This  is  the  only  adjustment  to  be  made.  It  will  be  noticed 
that  the  carbureters  used  on  the  Packard  and  Cadillac  auto- 
mobiles are  relatively  simple  in  the  arrangements  for  adjust- 
ment. 

Intake  Manifolds.  The  best  practice  is  to  place  the  car- 
bureter close  to  the  engine  cylinders  so  that  the  heat  from 
them  will  assist  in  securing  good  vaporization  of  the  gasoline. 


GASOLINE  CARBURETERS  95 

There  is  always  a  tendency  for  the  gasoline  vapor  from  the 
carbureter  to  condense  in  the  branched  pipe  called  the  intake 
manifold  through  which  it  goes  to  the  engine  cylinders. 
Automobile  designers  have,  therefore,  carefully  studied  the 
effect  of  shape  and  location  of  this  manifold  on  the  condition 
of  the  explosive  mixture.  A  short  straight  manifold  has 
obvious  advantages  over  a  longer  one  with  curved  parts  be- 
cause it  gives  less  opportunity  for  the  gasoline  in  the  explo- 
sive mixture  to  condense  and  accumulate  in  drops  on  the 
walls.  It  is  also  important  to  have  the  distance  approximately 
the  same  from  the  carbureter  to  each  of  the  engine  cylinders 
as  there  will  then  be  about  the  same  amount  of  explosive  mix- 
ture going  to  each  cylinder.  In  some  engines  which  have 
block  cylinders  the  manifold  is  made  as  a  part  of  the  casting 
including  the  cylinders.  The  intake  manifold  is  then  merely 
a  hollow  passage  in  the  side  of  the  cylinder  block.  This 
method  has  the  advantage  of  providing  a  very  short  intake 
manifold  and  because  of  its  being  a  part  of  the  cylinder 
block  is  in  an  excellent  position  to  receive  heat  from  the 
engine  cylinders.  When  this  method  is  used  the  carbureter 
can  be  attached  directly  to  the  cylinder  block. 

Another  method  of  applying  heat  for  the  improvement 
of  vaporization  in  the  intake  manifold  is  to  make  the  mani- 
fold with  a  sort  of  jacket  surrounding  it  either  for  its  whole 
length  or  for  only  a  part.  Connecting  pipes  are  provided  on 
this  jacket  to  provide  for  the  circulation  of  some  of  the  ex- 
haust gases  from  the  engine  exhaust  pipe  through  it.  When 
such  an  exhaust  gas  jacket  is  placed  around  only  a  small  part 
of  the  intake  manifold,  the  jacket  is  called  a  ''hot  spot," 
meaning  localized  heating  of  the  explosive  mixture.  Recently 
there  has  been  considerable  discussion  as  to  the  best  location 
of  these  exhaust  jackets  or  "hot  spots."  Obviously,  the  prin- 
cipal object  of  a  device  of  this  kind  is  to  prevent  the  conden- 
sation of  gasoline  and  also  to  re-evaporate  accumulated  drops. 
Such  re-evap*oration  is  likely  to  be  greatest  where  there  is  a 
change  of  direction  of  the  flow  of  the  explosive  mixture,  as, 
for  example,  where  the  pipe  from  the  carbureter  enters  the 


96  GASOLINE  AUTOMOBILES 

manifold  and  the  stream  divides  to  flow  to  the  branches. 
Fig.  84  shows  one  method  of  applying  an  exhaust  jacket 
where  the  carbureter  pipe  enters  the  manifold.  In  some  other 
designs,  the  exhaust  jacket  is  made  large  enough  to  surround 
the  pipe  from  the  carbureter  and  also  the  manifold  itself 
for  a  short  distance  from  the  place  where  it  branches.  It  is 
claimed,  however,  that  practically  all  the  condensation,  at 
least  of  that  part  which  accumulates  in  drops,  is  on  the  wall 
of  the  manifold  directly  opposite  the  opening  of  the  pipe 
from  the  carbureter  into  the  intake  manifold.  It  is  for  this 
reason  that  it  is  claimed  the  device  shown  in  Fig.  84  is  more 

Exhaust  Manifofcl 


ThroWe 


FIG.  84.— Hot-spot  Manifold. 

effective  in  general  service  than  devices  covering  a  greater 
portion  of  the  manifold  with  an  exhaust  jacket.  For  very 
good  reasons,  the  best  method  of  preventing  gasoline  accu- 
mulation in  drops  in  the  intake  manifold  is  by  heating  it  on 
its  bottom  side  by  the  exhaust  pipe  placed  closely  ~below  the 
intake  manifold.  There  is,  of  course,  always  the  disadvantage 
that  if  there  is  too  much  heated  surface  without  regula- 
tion, the  temperature  of  the  explosive  mixture  may  be- 
come much  too  high  in  warm  weather  for  efficient  engine 
operation. 

Hot-air  Attachment.     Except  in  very  hot  weather  the 
operation  of  a  carbureter  is  improved  by  supplying  heated 


GASOLINE  CARBURETERS  97 

air  as  it  improves  vaporization  of  gasoline.  A  great  many 
carbureters  are  provided  with  an  attachment  for  heat- 
ing the  air  which  goes  into  the  air  intake  of  the  car- 
bureter. This  is  usually  done  by  taking  it  through  a 
pipe  attachment  which  takes  to  the  carbureter,  air  which 
has  been  heated  by  contact  with  the  hot  exhaust  pipe 
of  the  engine.  Fig.  73  shows  an  attachment  of  this 
kind. 

Hot- water  Attachment.  For  the  same  reason  that  hot- 
air  attachments  are  used  on  carbureters,  some  carbureters 
are  provided  with  a  water  jacket  as  shown  on  the  Rayfield 
carbureter  in  Fig.  75.  Hot  water  from  the  supply  used  to 
cool  the  cylinders  of  the  engine  is  passed  through  this  jacket 
which  warms  the  air  before  and  as  it  passes  the  carbureter 
nozzle. 

Disadvantages  of  Hot-air  and  Hot-water  Carbureter 
Attachments.  In  order  to  avoid  the  difficulties  arising  from 
the  presence  of  unburned  gasoline  in  the  cylinder,  provision 
must  be  made  for  supplying  it  to  the  engine  cylinders  in 'a 
dry  or  completely  vaporized  condition.  The  simplest  method 
of  obtaining  complete  vaporization  is  by  making  provision 
for  heating  the  carbureter  either  by  using  the  hot  water 
from  the  engine  water  jacket  or  hot  gases  from  the  engine 
exhaust  pipe.  Neither  of  these  methods  is,  however,  alto- 
gether satisfactory  because  there  is  difficulty  in  regulating 
the  amount  of  heat  to  the  requirements.  When  the  engine 
is  operating  with  a  wide  open  throttle  valve  for  the  condi- 
tions of  either  high  speed  or  heavy  load,  either  of  these 
methods  will  give  a  great  deal  too  much  heat  to  the  car- 
bureter if  the  amount  is  adjusted  to  give  the  right  amount 
for  light  load  operation.  There  are  two  objectionable  fea- 
tures of  this  kind  of  carbureter  heating  when  the  throttle 
valve  is  more  than  half  way  open:  (1)  the  added  heat 
increases  the  volume  of  the  explosive  mixture  and  conse- 
quently reduces  the  weight  of  explosive  mixture  used  to 
such  an  extent  that  the  speed  of  the  engine  is  appreciably 
reduced;  (2)  the  heating  the  carbureter  raises  the  tempera- 


98  GASOLINE  AUTOMOBILES 

ture  of  the  explosive  mixture  so  high  that  with  the  further 
addition  of  heat  during  the  compression  stroke  in  the  en- 
gine, and  during  the  explosion  that  follows,  the  lighter 
petroleum  fuels  like  gasoline  will  be  broken  up  or  "dis- 
sociated" into  gases  having  hydrogen  as  the  important  con- 
stituent. This  hydrogen  when  undergoing  rapid  combustion 
because  of  its  high  heat  content  develops  a  great  amount 
of  energy  which  is  suddenly  applied  to  the  top  of  the  engine 
piston  and  produces  in  the  engine  what  we  call  "knocking." 

There  is  another  reason  why  the  adding  of  heat  to  the 
carbureter  is  objectionable  when  the  throttle  valve  is  more 
than  half-way  open,  and  more  especially  when  wide  open. 
Wide  open  throttle  valve  permits  the  maximum  amount  of 
explosive  mixture  to  enter  the  engine  cylinders  while  a 
partially  opened  throttle  reduces  the  amount  of  mixture 
going  to  the  cylinder.  It  is  obvious,  therefore,  that  with 
wide  open  throttle  with  its  large  amount  of  explosion  mix- 
ture, the  compression  in  the  cylinders  will  be  carried  to  a 
higher  pressure,  and  consequently  the  temperature  will  be 
higher  than  for  a  partly  opened  throttle  valve.  The  ideal 
arrangement  is,  obviously,  to  supply  only  enough  heat  to  a 
carbureter  when  the  throttle  valve  is  partly  opened  to  pro- 
duce a  thoroughly  vaporized  explosive  mixture  with  arrange- 
ments for  reducing  the  amount  of  heat  supplied  to  the  car- 
bureter when  the  throttle  valve  is  wide  open. 

Packard  Fuelizer.  Fig.  85  shows  in  considerable  detail 
the  type  of  apparatus  called  the  Packard  fuelizer  which 
has  been  developed  to  produce  complete  vaporization  of  the 
explosive  mixture  before  it  gets  to  the  engine  cylinder  and 
has  a  device  for  cutting  off  the  supply  of  heat  in  proportion 
to  the  amount  of  opening  of  the  engine  throttle  valve.  The 
principle  of  this  device  is  to  take  advantage  of  the  different 
pressures  on  the  two  sides  of  the  butterfly  throttle  valve 
in  the  carbureter  and  cause  a  small  amount  of  explosive 
mixture  to  go  through  an  auxiliary  passage  which  is  parallel 
to  the  main  intake  passage.  The  amount  of  mixture  going 
through  the  auxiliary  passage  is  set  on  fire  by  contact  with 


GASOLINE  CARBURETERS 


99 


the  sparks  from  a  spark  plug  with  the  result  that  intense 
heat  is  generated  in  this  auxiliary  passage  for  starting  and 
light  load  engine  conditions.  This  apparatus  will,  therefore, 
tend  to  improve  engine  efficiency  when  using  heavy  gasoline 
under  ''low  throttle"  and  light  load  when  an  intense  heat 
is  generated  in  a  part  of  the  explosive  mixture.  On  the 
other  hand  with  wide  open  throttle  conditions,  but  little  of  the 
explosive  mixture  passes  through  this  auxiliary  passage  and 


SparkPlug 


To  Engine  Irrhke 


Gasoline 


FIG.  85. — Packard  Carbureter  and  Fuelizer. 

almost  a  negligible  amount  of  heat  is  put  into  the  engine  cyl- 
inder. The  auxiliary  passage  carrying  explosive  mixture  from 
the  mixing  chamber  M  to  the  spark  plug  is  shown  at  the  right- 
hand  side  of  the  apparatus  and  is  marked  P.  The  actual 
construction  is  more  complicated  than  shown  in  the  figure 
but  enough  details  are  shown  to  indicate  the  method  of  opera- 
tion. It  should  be  clear  that  when  the  throttle  valve  is  in 
a  nearly  closed  position  as  indicated  in  the  figure  there  will 
be  a  very  small  flow  of  explosive  mixture  past  it,  and  the 
engine  suction  will  be  effected  mostly  by  the  flow  through 


100  GASOLINE  AUTOMOBILES 

the  auxiliary  passage  P  supplying  mixture  for  combustion 
at  the  spark  plug.  Opposite  the  spark  plug  is  the  observation 
window  0  of  heat-resisting  glass,  which  permits  the  action 
of  the  burner  to  be  observed  at  all  times.  Instead  of  actually 
taking  the  explosive  mixture  into  the  auxiliary  passage  P 
from  the  mixing  chamber  immediately  below  the  throttle  valve 
the  combustible  mixture  supplied  to  the  auxiliary  passage  is 
made  by  taking  gasoline  directly  from  the  carbureter  through 
the  small  capillary  tube  Q  and  mixing  it  with  air  taken 
through  the  pipe  Y  from  the  main  air  passage  A.  In  actual 
operation,  when  the  engine  is  idling,  combustion  takes  place 
in  the  burner  silently  and  continuously  and  a  bluish-green 
flame  completely  fills  the  combustion  chamber.  This  flame 
diminishes  in  intensity  as  the  throttle  is  opened,  with  the 
general  result  that  for  ordinary  driving  conditions  up  to 
about  twenty-five  miles  per  hour,  a  mixture  temperature 
of  150  to  180  degrees  Fahrenheit  is  maintained,  giving  per- 
fect distribution,  excellent  acceleration,  absence  of  spark-plug 
fouling  and  elimination  of  dilution  of  the  lubricant  in  the 
crankcase.  At  higher  speeds  and  wider  throttle  opening  the 
influence  of  the  fuelizer  gradually  decreases  until  at  wide-open 
throttle  it  is  practically  out  of  action,  which  is  exactly  the 
condition  desired.  This  combination  has  permitted  the  run- 
ning of  a  twelve-cylinder  engine  on  kerosene  at  moderate 
driving  speeds  with  practically  the  same  results  as  when 
using  gasoline,  but  when  using  kerosene  there  are  critical  tem- 
peratures below  which  we  cannot  go  without  considerable 
knocking. 

Suggestions  for  Successful  Carbureter  Operation.  It  is 
obviously  impossible  to  give  detailed  instructions  which  will 
answer  for  all  types  of  carbureters,  but  there  are  certain 
fundamental  principles  which  apply  to  the  adjustment  of  all 
types. 

There  are  numerous  troubles  coming  from  an  engine 
itself  or  its  auxiliaries  which  must  be  remedied  before  any 
adjustment  on  the  carbureter  can  be  satisfactorily  made. 
It  must  be  ascertained  (1)  whether  a  good  spark  occurs  in 


GASOLINE  CARBURETERS  101 

the  cylinder  at  the  proper  time;  (2)  whether  each  cylinder 
has  the  proper  compression;  (3)  whether  the  intake  mani- 
fold and  its  connections  to  the  carbureter  are  free  from 
air  leaks;  (4)  whether  gasoline  is  being  furnished  to  the 
carbureter  in  sufficient  amounts;  (5)  whether  the  carbureter 
is  free  from  water  and  dirt  in  the  bottom  of  the  float 
chamber. 

The  engine  must  be  warmed  to  normal  running  conditions 
before  any  adjustments  are  attempted.  The  engine  should 
be  run  idle  with  the  spark  retarded  and  the  throttle  open  only 
enough  for  moderate  engine  speed.  The  low-speed  adjust- 
ment, usually  on  the  gasoline,  is  made  so  that  the  engine 
explosions  are  regular,  after  which  the  spark  ignition  should 
be  set  for  high  speed  and  the  engine  speedd  up.  Th  high- 
speed adjustment,  usually  on  the  auxiliary  air  valve,  is  then 
made.  When  this  adjustment  is  correctly  made,  the  engine 
should  be  first  operated  slowly  and  then  the  throttle  valve 
should  be  opened  quickly  to  test  the  engine  for  uniformity  of 
explosions  with  rapid  acceleration.  If  upon  opening  the  throttle, 
the  engine  back-fires  or  "spits  back,"  the  mixture  is  weak 
and  the  gasoline  adjustment  should  be  made  to  provide  more 
fuel.  If  the  engine  is  to  be  run  at  practically  constant 
speed  there  is  little  need  of  quick  acceleration ;  the  most 
economical  adjustment  will  be  one  which  back-fires  occa- 
sionally on  rapid  acceleration.  "Choking"  in  the  car- 
bureter with  rapid  acceleration  indicates  too  rich  a 
mixture. 

A  rich  mixture  is  indicated  by  the  (1)  overheating  of 
the  cylinders,  (2)  waste  of  fuel,  (3)  "choking"  of  the  engine, 
(4)  misfiring  at  low  speeds,  (5)  heavy  black  exhaust  smoke 
with  a  very  disagreeable  odor. 

A  weak  mixture  manifests  itself  by  (1)  back-firing 
through  the  carbureter  and  (2)  by  loss  of  power.  Back- 
firing or  "popping  back"  through  the  carbureter  is  caused 
when  a  fresh  charge  of  explosive  mixture  enters  the  cylinder 
and  comes  into  contact  with  a  slow-burning  charge  left  in 
the  cylinder  from  the  preceding  power  stroke.  Under  these 


102  GASOLINE  AUTOMOBILES 

conditions,  since  the  intake  valve  is  open,  the  force  of  the 
explosion  comes  back  through  the  carbureter.  A  weak  mix- 
ture bums  slowly  and  is  likely  to  be  incompletely  burned 
when  the  fresh  charge  of  explosive  mixture  enters  the 
cylinder  on  the  next  suction  stroke.  Back-firing  may  be 
caused  also  by  leaky  intake  valves  in  the  engine  cylinder. 

Color  of  Exhaust.  A  proper  mixture  will  give  little  or 
no  smoke  at  the  exhaust.  Blue  smoke  is  caused  by  the 
burning  of  excess  lubricating  oil  and  has  no  relation  to  the 
quality  of  the  mixture.  Black  smoke  is  due  to  the  car- 
bureter being  set  for  too  rich  a  mixture.  White  exhaust 
in  cold  weather  is  due  to  a  small  amount  of  steam  in  the 
exhaust  gases  and  is  not  objectionable.  It  is  not  "smoke." 

An  easy  test  to  see  whether  the  carbureter  is  working 
right  is  to  run  several  blocks  with  the  throttle  practically 
closed,  then,  when  the  road  is  clear,  press  sharply  upon 
the  accelerator  pedal,  which  opens  the  throttle  wide  and 
should  make  the  engine  speed  up  and  the  automobile  "jump" 
forward.  If  it  is  sluggish  there  is  too  rich  a  mixture,  and  if 
it  sputters  and  perhaps  backfires,  it  is  too  weak. 

When  the  engine  is  running  slowly,  air  passes  through 
the  carbureter  so  slowly  that  the  gasoline  is  not  broken  up 
into  very  fine  particles,  consequently  it  does  not  fully  vaporize 
and  is  very  easily  condensed.  It  forms  liquid  gasoline  in  the 
intake  pipe  or  cylinder.  This  is  called  "loading  up"  and  is 
responsible  for  black  smoke  when  the  automobile  is  started. 

If  the  owner  will  make  sure  that  he  is  not  exhausting 
black  smoke  he  need  not  worry  about  the  price  of  gasoline, 
and  a  little  judgment  and  care  will  eliminate  many  of  the  items 
of  upkeep  expense. 

Wherever  there  is  a  leak  between  the  carbureter  and  the 
cylinder  it  lets  in  air  and  thins  the  mixture  so  that  it  is 
necessary  to  feed  in  more  gasoline  to  get  a  mixture  that  will 
fire  and  that  is  wasteful,  for  a  mixture  made  anywhere  else 
than  in  the  carbureter  is  less  efficient. 

It  takes  two  hundred  cubic  feet  of  air  to  a  pint  of  gasoline 
vaporized  to  produce  good  combustion,  though  the  air  supply 


GASOLINE  CARBURETERS  103 

is  usually  much  more  than  this  to  insure  carrying  off  the 
unburned  nitrogen  from  the  air.  For  starting  and  speeding 
up,  more  gasoline  is  admitted  to  the  vaporizing  chamber  as 
the  rich  mixture  ignites  more  quickly,  but  for  running,  a 
leaner  mixture  produces  better  results. 

The  adjustment  of  the  carbureter  should  not  be  changed 
unless  one  is  certain  that  it  is  wrong.  If  the  automobile  has 
been  running  with  the  carbureter  working  properly  and  no 
one  has  changed  the  adjustment,  it  may  safely  be  assumed,  in 
most  cases,  that  the  carbureter  adjustment  is  correct. 

On  a  dry,  warm  day  the  gasoline  vaporizes  easily  and 
the  maximum  charge  is  readily  exploded  in  the  cylinder, 
giving  maximum  power.  On  a  wet  cold  day  one  must  slightly 
decrease  the  supply  of  gasoline,  or  the  cylinders  will  "choke" 
and  the  engine  will  knock. 

When  the  heavier  grades  of  gasoline  as  now  sold  are  used 
in  an  automobile  engine  under  normal  operating  conditions, 
when  about  ninety  per  cent  of  the  time  the  engine  is 
running  under  a  light  load,  the  temperature  in  the  engine 
cylinders  is  not  high  enough  for  complete  vaporization  so 
that  some  of  the  unburned  part  is  being  deposited  con- 
tinuously on  the  spark  plugs  and  on  the  inside  of  the  cylinder 
in  the  form  of  soot.  Soot  deposited  on  the  spark  plugs 
has  the  effect  of  short  circuiting  the  parts  of  the.  spark 
plugs  which  should  be  electrically  insulated  from  each  other 
and  makes  them  useless  for  ignition.  These  soot  deposits  are 
called  "carbon." 

Some  of  this  unburned  portion  of  the  fuel  will  pass  the 
piston  in  the  liquid  condition  into  the  engine  crankcase 
where  it  mixes  with  the  lubricating  oil.  It  is  not  unusual 
to  hear  of  automobile  engines  which  after  traveling  a  few 
hundred  miles  will  have  in  their  crankcases  a  mixture  of 
gasoline  and  lubricating  oil  which  gives  extremely  poor 
lubrication,  'so  that  continued  running  without  its  removal 
will  result  in  burned  out  bearings,  scored  cylinders,  and 
other  automobile  difficulties  arising  from  improper  lubrica- 
tion. 


CHAPTER  V 
AUTOMOBILE  IGNITION 

When  the  explosive  mixture  of  gasoline  vapor  and  air 
enters  the  cylinder  of  the  engine,  it  must  be  ignited ;  and, 
in  automobile  engines,  the  usual  method  of  ignition  is  by 
means  of  an  electric  spark.  Most  of  the  devices  for  making 
and  timing  the  electric  spark  are  complicated.  It  is  neces- 
sary, therefore,  to  know  the  basic  principles  because  most 
of  the  serious  troubles  with  a  modern  automobile,  excluding 
the  tires,  are  with  the  electrical  equipment.  If  the  "spark" 
does  not  come  right  or  does  not  come  at  all,  there  is  real 
trouble. 

Electricity.  Very  little  is  known  regarding  the  "sub- 
stance" of  electricity.  In  this  respect  it  is  almost  as  much 
of  a  mystery  today  as  when  Benjamin  Franklin  took  a  spark 
from  the  clouds  with  his  silk  kite  and  string.  On  the 
other  hand,  the  laws  of  the  behavior  of  electricity  under 
almost  any  conditions  are  well  established. 

Electrical  Pressure  or  Voltage.  Like  air,  or  water,  elec- 
tricity flows  from  a  position  of  high  pressure  to  one  of  low 
pressure.  There  must  be  pressure  for  electricity  to  be  car- 
ried on  wires  the  same  as  it  is  necessary  to  have  pressure 
to  force  water  through  pipes.  Electrical  pressure  is  measured 
in  units  called  volts.  Thus,  if  at  one  point  the  electrical 
pressure  is  ten  volts  and  at  another  point  it  is  six  volts,  the 
pressure  difference  between  the  two  points  is  four  volts.  Now, 
if  a  metal  wire  is  stretched  between  the  two  points  an  electric 
current  will  flow  from  the  point  of  high  to  the  point  of  low 
voltage.  Electricity  flows  through  some  metals,  especially 
copper,  with  very  little  resistance;  while  substances  like  rub- 
ber, porcelain,  glass,  fiber  and  any  kind  of  gas  (including 
104 


AUTOMOBILE  IGNITION  105 

air)  offer  very  high  resistance  and  are  called  electric 
insulators.  Most  metals  offer  little  resistance  to  the  flow  of 
electricity.  Cotton,  silk,  or  rubber  coverings  on  wires  are 
to  insulate  them  from  each  other  and  from  other  electric 
conducting  materials.  Insulating  materials  are  used  as  cover- 
ings for  electric  wires  which  are  close  together  to  prevent 
the  current  from  flowing  from  one  wire  to  the  other,  or  to 
prevent  short-circuiting  the  wires.  The  insulation  on  wires 
should  not  rub  on  other  wires  or  on  metal  parts  of  an  auto- 
mobile, as  continued  rubbing  may  wear  through  the  insulation 
and  cause  short-circuiting. 

The  quantity  of  electricity  passing  over  a  wire  is  called 
the  current,  and  the  unit  of  measurement  of  this  current 
is  an  ampere.  In  the  flow  of  water  the  quantity  is  expressed 
in  gallons  per  hour,  while  in  the  flow  of  electricity  the 
quantity  is  expressed  in  amperes  per  hour  or,  for  short, 
ampere-hours.  Flowing  electric  current  must  always  have  a 
circuit  either  through  wires  or  through  metal  parts  of  an 
engine.  If  the  circuit  is  interrupted  or  "broken"  by  a  broken 
wire  or  by  an  open  switch,  the  current  cannot  go  through. 

Electric  Batteries  for  automobile  ignition  are  of  two 
distinct  kinds:  (1)  dry  cells  or  batteries;  and  (2)  storage, 
batteries. 

Dry  Cells  are  sometimes  used,  especially  on  small  auto- 
mobiles, as  a  source  of  electric  current  for  ignition. 
Although  soon  worn  out  in  the  usual  ignition  service,  they 
are  relatively  cheap  and  are  easily  replaced.  Fig.  86  shows 
a  typical  dry  cell  as  it  appears  when  cut  open  through  the 
middle  (in  cross  section).  The  outside  cylindrical  casing 
is  made  of  zinc.  Inside  of  this  casing  is  fitted  a  piece  of 
absorbent  paper  saturated  with  zinc  chemicals  and  plaster 
of  Paris.  In  the  middle  of  the  cell  is  a  stick  of  pure  carbon. 
The  space  between  the  absorbent  paper  and  the  carbon  stick 
is  filled  with  powdered  carbon  and  manganese  oxide.  To 
prevent  drying  out  of  the  saturated  paper,  the  top  of  the 
cell  is  sealed  air-tight  with  a  tar  compound.  The  electric 
pressure,  or  voltage,  of  a  good  dry  cell  is  about  1.5  volts. 


106 


GASOLINE  AUTOMOBILES 


The  maximum  possible  current  on  short  circuit  (as  a  dealer 
tests  it)  is  from  twenty  to  thirty-fire  amperes,  depending 
somewhat  on  the  size  of  the  cell.  The  carbon  terminal  is 
often  marked  with  the  symbol  +.  The  zinc  casing  must 
have  on  the  outside  a  covering  (side  and  bottom)  of  in- 
sulating material.  Heavy  paper  is  a  satisfactory  material, 
if  kept  dry. 

When  a  dry  cell  is  nearly  exhausted  its  useful  service 
can  usually  be  extended  by  making  a  small  hole  in  the 


Zinc  Terminal \      Carbon     Tertnfna/ 


Carbon 


Powdered 
Car  bo  none/1 
Manganese 


Pasteboard 
Casing 


FIG.  86.— Dry  Cell. 

top  and  pouring  in  a  little  water.  If  a  dry  cell  gives  out 
suddenly  on  the  road,  this  is  a  convenient  makeshift.  When 
running  an  automobile  with  any  kind  of  ignition  system, 
it  is  generally  a  convenience  to  have  a  few  good  dry  cells 
stored  away  for  emergency  service.  The  length  of  time  a 
dry  cell  can  be  used  depends  largely  on  the  kind  of  service. 
For  intermittent  service,  for  which  it  is  intended,  a  dry 
cell  will  usually  last  several  months.  For  diagrams  showing 
different  connections  of  dry  cells,  see  Figs.  92  and  93. 

Storage   Batteries.     Storage   batteries   differ  from   dry 
cells  in  having  a  liquid  solution.    A  typical  storage  battery 


AUTOMOBILE  IGNITION 


107 


as  shown  in  Fig.  87  consists  of  two  sets  of  lead  plates  made 
like  gridirons  placed  in  a  container  filled  with  a  solution 
of  weak  sulphuric  acid  and  water.  One  set  of  plates  has  the 
spaces  in  the  grids  filled  with  lead  peroxide  (brown  color). 
The  other  .set  of  plates  has  the  spaces  filled  with  ' '  sponge ' ' 
lead  (ordinary  lead  color).  These  plates  are  placed  in 
the  container  so  that  the  two  kinds  of  plates  alternate 
and  are  separated  from  each  other  by  perforated  pieces  of 
hard  rubber  or  of  wood  treated  to  withstand  the  acid.  All 
the  lead  peroxide  plates  are  connected  together  at  the  top 


Hare/rubber  Coyer        Battery  Terminals --^ 
Plastic  Sea  I  ing 


•  Trecrhed 'Hare/wood 
Case  w+h  Dovetviljoiirk 


^"'Gridiron  Plates 


Supports  of  Hard 
Rubber 

Mud  Space  to  Hold 
Sediment  from  P/a+es 


FIG.  87. — Storage  Cell  or  "Battery." 

by  a  metallic  lead  yoke  marked  the  (positive)  terminal. 
The  "sponge"  lead  plates  are  similarly  connected  by  a 
yoke  marked  the  (negative)  terminal.  The  terminals  of 
most  storage  batteries  are  marked  so  that  if  the  battery 
is  disconnected  from  the  wiring  system  of  an  automobile 
and  is  taken  out,  there  will  be  no  mistake  in  getting  the 
right  connections  when  putting  it  back.  If  it  is  put  back 
the  wrong  way,  it  will  be  discharging  instead  of  charging 
when  the  automobile  engine  is  running. 

Charging  and  Discharging   Storage  Batteries.     If  the 
-f-  terminal  of  the  storage  battery  is  connected  to  the  +  ter- 


108  GASOLINE  AUTOMOBILES 

minal  of  a  source  of  electric  current,  and  the  —  terminal  of  the 
battery  to  the  —  terminal  of  the  source,  the  electric  current 
passing  through  the  plates  and  through  the  acid  solution 
will  make  a  chemical  change  in  the  lead  peroxide  and  will 
deposit  it  on  the  "sponge"  lead  plate.  When  the  charging 
current  is  stopped  and  the  storage  battery  is  connected  up 
for  supplying  electric  current,  as  for  example,  for  starting 
an  automobile  engine,  it  is  said  to  be  discharging,  and  the 
chemical  change  in  the  battery  is  reversed;  that  is,  the 
"sponge"  lead  is  changed  chemically  and  deposited  again 
on  the  lead  peroxide  plate. 

All  the  plates  connected  with  a  set  of  yokes,  together 
with  their  container,  are  called  a  storage  cell.  Technically, 
a  group  of  cells  is  called  a  storage  battery.  The  container 
or  jar  must  be  of  some  good  insulating  material  like  hard 
rubber  or  glass. 

Charging  Test.  A  single  storage  cell  when  fully  charged 
by  electric  current  gives  an  electric  "pressure"  of  about  two 
volts.  Most  storage  batteries  consist  of  three  cells  and  give, 
therefore,  six  volts.  The  usual  method  of  testing  for  com- 
pleteness of  electric  charging  is  to  determine  the  specific 
gravity  of  the  acid  solution  in  the  container.  "When  satis- 
factorily charged,  the  specific  gravity  (see  page  111)  should 
be  between  1.27  and  1.30,  ordinarily  read  "1270"  and  "1300." 
The  discharge  of  electric  current  from  a  storage  cell  reduces 
the  specific  gravity  of  the  acid  solution  and  should  be  stopped 
if  the  specific  gravity  gets  as  low  as  1.15.  If  the  storage 
cells  are  used  for  electric  lights  as  well  as  for  ignition,  at 
this  stage  of  discharge  the  lights  will  not  have  their  usual 
brilliancy. 

Refilling  Battery  Solution.  The  acid  solution  should 
always  cover  at  least  the  "gridded"  part  of  the  lead  plates, 
and  it  is  a  good  rule  to  inspect  and  refill  each  storage  cell 
every  two  weeks.  There  is  always  some  loss  from  the  solution 
by  evaporation  and  spilling  if  roughly  handled.  After  refill- 
ing, the  level  of  the  solution  in  the  container  should  be  about 
the  level  of  the  bottom  of  the  filling  tube  or  filling  chamber. 


AUTOMOBILE  IGNITION  109 

Use  only  distilled  water  such  as  can  be  obtained  at  a  drug 
store  or  at  an  artificial  ice  plant.  Persons  of  ordinary  experi- 
ence should  never  add  any  acid  for  refilling.  In  emergencies 
melted  artificial  ice  or  fresh  rain  water  caught  in  a  glass  or 
crockery  receptacle  may  be  safely  used.  Ordinarily  only 
a  few  spoonfuls  of  water  are  needed  for  refilling.  If  one 
of  the  cells  always  requires  very  much  more  distilled  water 
for  refilling  than  the  others,  it  is  likely  there  is  a  leak  in 
the  container  or  jar  of  the  cell,  and  it  is  best  to  purchase  a 
new  container.  The  rubber  plugs  of  the  filling  tubes  should  be 
screwed  carefully  in  place  after  refilling. 

A  supply  of  distilled  water  for  refilling  should  be  kept 
in  a  large  glass  bottle  and  not  in  a  metal  bucket  or  can. 
Extreme  care  should  be  observed  to  keep  all  traces  of  metal 
out  of  the  storage  cells.  Water  from  wells,  springs,  or  city 
supplies  is  likely  to  contain  traces  of  metal  ores  and  other 
substances  which  will  rapidly  impair  storage  cells.  All 
automobile  storage  batteries  have  more  than  one  cell,  so 
that  refilling  at  one  filling  tube  provides  for  only  one  cell. 
Each  cell  should  be  inspected  regularly  and  refilled  as 
necessary. 

Transferring  the  lead  plates  from  one  container  to  an- 
other is  not  an  easy  matter,  as  the  lead  peroxide  plates  are 
fragile.  Such  work  should  be  done  by  a  person  experienced 
in  battery -repairing. 

Instruction  books  furnished  by  the  manufacturers  of 
storage  batteries  should  be  consulted  in  the  unusual  emer- 
gencies of  making  up  new  acid  solution  in  case  of  a  broken 
container,  or  of  "overcharging"  a  cell  when  it  is  to  be 
stored  and  is  not  to  be  used  for  several  months.  Storage 
cells  will  give  their  most  satisfactory  service  when  in 
moderate,  continuous  use,  so  as  to  be  kept  well  charged. 
Most  people  are  too  careless  in  the  use  of  storage  batteries 
to  get  the  best  service.  The  vibration  caused  by  fast  driving 
over  rough  roads  is  injurious  to  storage  batteries. 

Sulphating  of  Battery  Plates.  If  the  lead  plates  of  a 
storage  cell  are  not  kept  covered  with  the  acid  solution 


110  GASOLINE  AUTOMOBILES 

by  regular  filling,  the  plates  become  dry,  and  will  accumu- 
late a  whitish  material  (lead  sulphate).  When  the  forma- 
tion of  this  sulphate  is  once  started  it  tends  to  accumulate 
rapidly  and  by  causing  deterioration  of  the  plates  reduces 
the  capacity  of  the  battery.  When  there  is  any  considerable 
sulphate  accumulation,  it  is  time  to  think  of  saving  the 
cell  by  taking  it  to  the  battery  "service"  station  for  repairs. 
Sulphating  results  also  if  a  storage  cell  is  kept  in  storage 
when  not  fully  charged. 

Freezing  of  the  acid  solution  in  a  storage  cell  is  prevented 
by  keeping  it  fully  charged  as  the  following  table  shows: 

Amount  of  Charge  Specific  Gravity      Temp,  of  Freezing 

Fully  charged   1.27  to  1.29       No  danger  of  freezing 

Partly  discharged    1.20  15°  below  zero  Fahren- 

heit 
Not   dangerously   discharged...  1.15  0°  Fahrenheit 

Dangerously   discharged    1.12  30°  Fahrenheit  (about 

freezing  temperature 
of  water) 

Testing  a  storage  battery  with  a  hydrometer  is  the  only 
simple  method  to  determine  whether  it  is  in  good  condition 
for  service.  If  the  lights  connected  to  a  storage  battery  are 
dim  or  do  not  light  up  at  all,  but  on  the  other  hand  the 
hydrometer  test  is  1200  or  over,  it  is  likely  that  the  trouble 
is  with  the  connections  rather  than  the  battery.  If  pulling 
lightly  by  hand  on  the  wires  connecting  the  battery  to  the 
switches  on  the  instrument  board  makes  variable  brilliancy 
of  the  lights,  the  trouble  is  obviously  with  the  wiring  or  with 
the  connections.  Sometimes  there  is  a  little  deposit  of  sul- 
phate on  the  bolts  and  connections  where  the  heavy  wires  are 
attached  to  the  battery.  A  film  of  sulphate  makes  a  very 
poor  electrical  contact  and  will  often  interrupt  the  current. 

Whenever  a  storage  battery  is  removed  for  recharging  or 
for  winter  storage,  the  bolts  which  are  used  to  fasten  the 
wires  to  the  battery  terminals  should  be  cleaned  and  covered 
with  a  little  vaseline,  when  the  battery  is  replaced  in  the  auto- 


AUTOMOBILE  IGNITION 


111 


mobile  and  the  wires  are  again  fastened.  If  a  little  vaseline 
is  put  on  the  battery  connections  from  time  to  time,  accu- 
mulation of  sulphate  will  usually  be  prevented. 

Storage  Battery  Hydrometers.    A  convenient  device  for 
determining  the  specific  gravity  of  the  acid  solution  in  storage 


•"1.300 


FIG.  88.— Storage  Battery  Hydrometer. 

batteries  is  shown  in  Fig.  88.  It  consists  of  a  rubber-bulb 
syringe  with  a  long  glass  chamber  in  which  a  very  small 
hydrometer  is  placed.  To  Use  this  device  the  air  is  first 
expelled  by  hand  pressure  on  the  rubber  bulb,  and  then  when 
the  narrow  stem  is  put  into  the  filling  tube  of  the  cell  to 


112  GASOLINE  AUTOMOBILES 

be  tested,  the  hand  pressure  on  the  bulb  is  released.  By 
this  operation  some  of  the  acid  solution  from  the  cell  will 
be  drawn  by  suction  into  the  glass  chamber.  The  hydrometer 
inside  the  glass  chamber  will  float  in  the  solution,  and  the 
reading  on  its  scale  at  the  surface  of  the  liquid  denotes  the 
specific  gravity.  The  sample  of  the  solution  should  be  care- 
fully put  back  into  the  same  cell  from  which  it  was  taken. 
This  is  easily  done  by  again  putting  the  narrow  stem  of  the 
syringe  into  the  filling  tube  of  the  cell  and  pressing  on  the 
rubber  bulb  till  all  the  solution  is  forced  out. 

Direct  and  Alternating  Current.  There  are  two  kinds 
of  current  obtainable  for  electrical  services:  (1)  direct  cur- 
rent, and  (2)  alternating  current.  Direct  current  always 
flows  continuously  in  one  direction  through  its  conductor, 
which  is  commonly  a  wire.  Every  kind  of  electric  battery 
generates  direct  current.  In  charging  and  recharging  storage 
batteries  only  direct  current  is  used.  Alternating  current, 
on  the  other  hand,  is  constantly  reversing  its  direction,  flow- 
ing first  in  one  direction  and  then  in  the  other.  The  changes 
in  direction  are  very  rapid,  running  into  hundreds  per  minute. 
Rectifier  for  Alternating  Current.  Before  alternating 
current  may  be  used  in  charging  storage  batteries  it  is  changed 
to  direct  current  by  a  device  called  a  rectifier.  A  rectifier 
made  by  the  General  Electric  Company  for  connection  to 
an  electric  lamp  socket  is  shown  in  Fig.  89.  Such  rectifiers 
are  usually  designed  to  give  a  charging  current  of  about  four 
amperes  for  the  three  to  six  cells  in  an  automobile  storage 
battery.  A  small  apparatus  of  this  kind  suitable  for  use 
in  a  small  garage  can  be  purchased  for  about  fifteen  dollars. 
Charging  Storage  Batteries  with  Lighting  Current. 
Where  direct  current  is  furnished  by  local  light  and  power 
plants*  a  rectifier  is  unnecessary  in  charging  storage  bat- 
teries. The  voltage  of  the  local  lighting  system  (usually  110 
volts)  is  ordinarily  too  high  for  charging  purposes,  for  if 

*  The  kind  of  current  furnished  may  be  learned   by  inquiry  at  the 
electric  light  plant. 


AUTOMOBILE  IGNITION 


113 


a  storage  battery  is  connected  to  the  wires  which  supply  an 
electric  lamp,  an  enormously  large  current  will  go  through 
the  battery.  Making  wire  connections  under  such  conditions 
is  dangerous  work  for  the  operator;  besides  the  heavy 
current  may  ruin  the  battery.  The  use  of  ordinary  direct 
current  may  be  made  fairly  safe,  however,  by  installing  a 
row  of  lamps  between  the  charging  wire  and  the  battery. 
This  may  be  done  by  arranging  a  set  of  eight  electric  lamps 
(either  50-watt  or  16-candle  power  carbon  lamps),  and  con- 


A!ferr?at/'r?q  Current 
'Line  Wires 


Regulating 
Switch-"'1' 


Mercury  Bulb 


Lamp  Socket 

^• 


Wires 


FIG.  89.  —  Mercury  Rectifier  for  Alternating  Current. 

necting  them  as  shown  in  Fig.  90  to  the  terminals  of  a 
storage  battery.  If  25-watt  tungsten  lamps  are  used  instead 
of  50-watt  lamps,  there  must  be  sixteen  lamps  instead  of 
eight  in  order  to  get  the  same  amount  of  charging  current 
—  about  four  ampej»es.  On  the  other  hand,  it  is  possible 
to  do  the  charging  with  only  eight  25-watt  lamps  in  twice 
the  time.  For  the  set  of  lamps  shown  in  the  figure  it  will 
take  from  24  to  30  hours  to  fully  charge  a  battery  of  cells 
which  have  been  run  down  to  a  specific  gravity  of  about 
1.15,  or  from  48  to  60  hours  with  eight  25-watt  lamps.  The 


114 


GASOLINE  AUTOMOBILES 


charging  need  not  be  done  at  one  time;  part  of  the  charge 
may  be  given  one  day  and  more  another  day. 

Direction  of  Charging.  For  charging  a  storage  battery 
its  +  terminal  must  be  connected  to  the  -}-  wire  of  the 
lighting  circuit,  and  its  —  terminal  to  the  —  wire.  Other- 
wise, if  it  were  connected  to  the  lighting  circuit  +  to  — , 
and  —  to  -J-,  the  lighting  circuit  would  be  taking  current 


FIG.  90.— Electric  Lamp  Device  for  Charging. 

out  of  the  battery  instead  of  sending  current  through  it 
to  make  the  chemical  changes  in  the  lead  plates  necessary 
for  charging.  The  +'  and  -  terminals  of  a  storage  battery 
are  usually  plainly  marked.  The  +  and  -  terminals  of 
battery  or  line  wires  are  easily  determined  by  a  simple  test 
the  principle  of  which  is  shown  in  Fig.  91.  First  remove 
all  insulating  material  from  the  end  of  each  wire.  Scrape 
the  exposed  wire  until  bright.  Then  dip  the  two  ends  into  a 


•AUTOMOBILE  IGNITION 


115 


cup  of  water  to  which  a  tablespoonful  of  common  salt  has  been 
added.  If  the  ends  are  held  about  one-quarter  inch  apart 
in  this  salt  water  solution,  small  bubbles  will  rise  from  the 
wire  which  is  the  —  (negative)  terminal.  This  is  the  wire 
to  be  attached  to  the  —  terminal  of  the  battery  for  charging. 
The  other  wire  is  -j-  (positive)  and  should  be  connected  to 
the  -j-  terminal  of  the  battery.  When  making  this  test  if 


Hyd 
Gaa  Bubblee\ 


FIG.  91.—  Testing  Electric  Wires. 

the  bubbles  do  not  appear,  the  wiring  may  be  defective  and 
an  expert  should  be  consulted. 

Series  and  Parallel  Connections.  As  a  single  storage  or 
dry  cell  gives  too  little  voltage  for  practical  purposes  in  auto- 
mobile operation,  several  cells  must  be  connected  together  to 
get  the  necessary  voltage  for  ignition,  lighting  and  start- 


FIG.  92. — Cells  in  Series. 


ing;  that  is,  to  get  from  six  to  eight  volts.  The  way 
four  dry  cells  of  one  and  a  half  volts  each  can  be  connected 
to  get  a  total  of  six  volts  is  shown  diagrammatically  in 
Fig.  92.  By  this  arrangement  the  carbon  terminal  (-)-) 
of  one  cell  is  connected  to  the  zinc  terminal  ( — )  of  the 
next.  This  is  called  connecting  the  cells  in  series.  By  this 
method  the  volts  of  the  individual  cells  are  combined,  or  the 


116  GASOLINE  AUTOMOBILES 

total  voltage  is  equal  to  the  number  of  cells  multiplied  by 
the  volts  of  each  cell.  A  dry  ceU  is  tested  for  amperes, 
by  connecting  its  two  terminals  together  by  an  instrument 
(ammeter).  It  is  safe  to  do  this  with  a  dry  cell  but  should 
never  be  attempted  with  a  storage  cell  because  the  latter 
can  give  an  enormous  and  dangerous  current  when  short  cir- 
cuited. 

If  all  the  carbon  positive  (  +  )  terminals  are  connected 
together  and  similarly  all  the  zinc  negative  (  — )  terminals, 
as  in  Fig.  93,  the  four  cells  are  connected  in  parallel.  In 
this  way  the  amount  of  current  is  increased  and  the  total 
amperes  of  the  set  is  equal  to  the  amperes  of  one  cell  multi- 


X^fc/          Xu»/         \W^          N*^          N  **«.-.. 

FIG.  93.— Cells  in  Parallel. 

plied  by  the  number  of  cells.  The  volts  are  the  same  as  of 
one  cell. 

The  following  brief  rule  is  easily  remembered.  To  increase 
the  volts  or  voltage,  connect  the  cells  together  in  a  series 
arrangement,  as  in  Pig.  92.  To  increase  the  amperes  or 
amount  of  current,  connect  the  cells  in  parallel,  as  in  Fig.  93. 

Magnetism  and  Electricity.  In  order  to  have  a  clear 
understanding  of  the  electrical  apparatus  used  in  auto- 
mobiles, one  should  know  the  relation  between  magnet- 
ism and  electricity.  Magnetism  suggests  the  attraction 
of  pieces  of  iron  or  steel  to  a  magnet.  The  field  of 
influence,  called  the  magnetic  field,  of  a  magnet  is  strongest 
at  its  ends.  The  close  relation  of  electricity  to  magnetism 
is  easily  shown  by  winding  a  wire  carrying  an  electric  current 
around  a  bar  of  iron  and  observing  the  magnetization  of  the 


AUTOMOBILE  IGNITION 


117 


iron.  This  is  illustrated  in  Fig.  94  where  a  bar  of  iron  M  is 
shown  with  a  coiled  wire  C  around  it,  taking  current  from 
the  battery  B.  The  current  in  the  coil  makes  a  magnet  of  the 
iron  bar  M  and  produces  around  the  magnet  the  magnetic 
field  shown  by  the  light  dotted  lines  extending  from  one  end 
of  the  bar  to  the  other.  The  iron  bar  with  the  encircling  coil 
is  called  an  electro-magnet  to  distinguish  it  from  a  permanent 
magnet. 

If  any  conductor  of  electricity,  as  for  example,  the  wire 
loop  L  in  Fig.  94  is  moved  in  any  part  of  the  magnetic 
field,  a  current  of  electricity  will  be  made  to  flow  through 
the  conductor,  in  this  case  the  wire  loop.  Similarly,  a  current 


FIG.  94.— Magnetic  Field. 

of  electricity  is  produced  if  the  wire  loop  is  held  stationary 
and  a  magnet  is  moved  back  and  forth  near  it.  Also  if  the 
electric  current  in  the  coil  C,  wound  on  the  bar  M  is  alternately 
"broken"  and  "made"  (by  the  switch  at  S)  a  momentary 
electric  current  will  flow  in  the  wire  loop  L  when  placed 
as  shown  at  one  end  of  the  bar. 

Now,  the  same  electrical  effect  observed  with  the  loop  L, 
when  held  at  the  end  of  the  magnet  M,  can  be  obtained  by 
winding  a  second  coil  of  wire  8  on  top  of  the  coil  C,  as 
shown  in  Fig.  95.  An  electric  current  will  be  made  to  flow 
through  the  coil  8  when  the  current  through  the  coil  C  is 
alternately  ' '  made ' '  or  ' '  broken. ' '  The  voltage  of  the  induced 
current,  as  it  is  called,  in  the  coil  8  will  be  the  same  as  the 


118 


GASOLINE  AUTOMOBILES 


voltage  in  the  coil  C  if  the  number  of  turns  or  rings  is  the 
same  in  each  coil.  If,  however,  the  numbers  of  turns  in  the 
coil  S  is  ten  thousand  times  as  large  as  the  number  of  turns 
in  the  coil  C,  then  the  voltage  in  S  is  ten  thousand  times  as 
large  as  that  in  C.  A  large  quantity  of  current  (aniperes) 


FIG.  95. — Simple  Induction  Coil. 

at  the  high,  voltage  produced  by  such  a  coil  would  be  danger- 
ous, but  there  is  only  a  small  current  in  any  device  of  this 
kind  likely  to  be  used  on  an  automobile,  so  that  a  shock  from 
it  will  give  only  an  uncomfortable  feeling.  But  do  not  ever 
connect  together  (short  circuit)  the  terminals  of  a  storage 


FIG.  96. — Winding  of  Wires  for  Inducing  High- 
Voltage  Current. 

battery.    Fig.  96  shows  very  clearly  the  arrangement  of  wires 
inducing  a  high  voltage  current. 

The  necessary  electric  spark  for  practically  all  kinds  of 
automobile  engine  ignition  is  obtained  by  means  of  an  electric 
current  which  is  made  to  jump  across  the  air  gap  between 


AUTOMOBILE  IGNITION  119 

the  points  of  two  electric  wires  of  an  ignition  device  called 
a  spark  plug.  In  order  to  make  electricity  jump  across  the 
air  gap  in  a  spark  plug  a  high  electric  pressure  of  at  least 
nine  thousand  volts  is  needed.  Most  ignition  systems  using 
batteries  have  three  storage  cells  or  six  dry  cells.  Six  dry 
cells,  for  example,  can  give  when  new  only  about  nine  volts, 
and  this  low  voltage,  therefore,  must  be  raised  to  nine  thou- 
sand volts  to  force  an  electric  spark  with  certainty  across  a 
one  thirty-second  inch  air  gap  of  a  spark  plug.  In  practically 
all  appliances  using  electric  current  from  batteries  for  engine 
ignition  by  means  of  spark  plugs,  the  necessary  increase  in 
voltage  is  obtained  by  the  use  of  a  coil  like  S  in  Fig.  95, 
having  a  large  number  of  turns.  By  this  method,  the  required 
nine  thousand  volts  can  be  obtained  from  six  dry  cells  (nine 
volts)  by  the  use  of  a  device  similar  to  the  one  shown,  having 
one  thousand  times  as  many  turns  on  the  coil  S  as  on  the 
coil  C*  For  practical  reasons  the  low  voltage  coil  C  is  made 
of  coarse  wire  and  the  high  voltage  coil  8  of  fine  wire. 

Spark  Plugs.  A  spark  plug  has  for  its  essential  parts  two 
wires  which  are  thoroughly  insulated  electrically  from  each 
other  and  are  close  enough  together  at  their  ends  to  make  a 
short  air  gap.  Except  for  minor  details,  the  construction 
of  all  kinds  of  spark  plugs  is  about  the  same.  The  one  shown 
in  Fig.  97  is  an  example  of  standard  construction.  The 
wire  which  brings  the  high  voltage  electric  current  from  the 
fine-wire  winding  of  the  induction  coil  S  (Fig.  95)  to  the  spark 
plug,  is  fastened  to  the  top  T,  so  as  to  make  electrical  contact 
with  a  wire  W,  made  of  special  heat-resisting  nickel  steel 
alloy.  This  wire  W  extends  down  through  the  central  por- 
tion or  core,  which  is  made  of  porcelain  or  mica.  Outside 
the  central  core  is  a  steel  ring  or  "body  "  B  with  a  screw  thread 
to  which  is  attached  a  curved  wire  V  which  projects  inward 


*  The  electrical  principles  involved  are  general  in  application ;  that 
is,  the  voltage  in  the  coil  -S  (called  the  secondary)  is  to  the  voltage  in 
the  coil  C  (called  the  primary)  as  the  number  of  turns  in  S  is  to  the 
number  of  turns  in  C. 


120 


GASOLINE  AUTOMOBILES 


toward  the  straight  central  wire  W.     The  distance  between 
the  tips  of  these  two  wires,  making  the  air  gap  is  usually 


FIG.  97.— Parts  of  a  Spark  Plug. 

about  one  thirty-second  of  an  inch  (the  thickness  of  a  worn 
dime).  The  porcelain  or  mica  core  insulates  electrically  the 
two  wires  W  and  V.  The  electrical  resistance  of  mica 


FIG.  98. — Two  "Point"  Spark  Plug. 

breaks  down  in  the  presence  of  oil  so  that  it  is  not  much  used. 
The  metal  ring  or  "body"  is  threaded  so  that  it  can  be 
screwed  into  the  top  of  an  engine  cylinder.  A  slightly  dif- 


AUTOMOBILE  IGNITION 


121 


ferent  spark  plug  with  two  " points"  or  air  gaps  is  shown  in 
Fig.  98.    A  more  commonly  used  type  is  shown  in  Fig.  99. 


Afr&ap.. 

FIG.  99.— Single  "Point' 


Spark  Plug. 


Battery  Ignition  Systems.  The  outline  drawing  shown 
in  Fig.  95  shows  the  essential  parts  of  all  modern  battery 
ignition  systems.  It  includes  a  battery,  an  induction  coil 
with  windings  of  coarse  and  fine  wire,  a  circuit  breaker  or 
switch  with  movable  contact  points,  and  a  spark  plug  with 
the  wires  for  connecting  these  parts  as  they  might  be  applied 
to  a  single  cylinder  engine.  Practically  all  automobile  engines, 
however,  have  four  or  more  cylinders,  and  each  cylinder 
requires  a  separate  device  for  the  ignition  of  the  explosive 
mixture.  Figs.  100  and  101  show  a  diagram  of  a  typical 
battery  ignition  system  for  a  four  cylinder  engine.  The  top 
view  of  this  diagram  (Fig.  100)  shows  the  arrangement  of 
wires  carrying  the  high-voltage  current  from  the  device 
called  the  distributor  to  the  individual  spark  plugs.  The 
order  of  numbers  on  the  distributor  is  not  the  same  as  the 
consecutive  numbers  on  the  spark  plugs.  There  is  this  differ- 
ence in  numbering  because  the  distributor  determines  the  fir- 
ing order  of  the  cylinders.  (See  page  45.)  Below  this  draw- 
ing of  the  distributor  is  a  side  view  (Fig.  101)  of  a  complete 
ignition  device.  The  top  of  this  view  shows  again  the  dis- 


122 


GASOLINE  AUTOMOBILES 


tributor  with  its  central  wire  carrying  the  high  voltage  cur- 
rent from  the  induction  coil,  and  the  wires  from  the  dis- 
tributor to  the  spark  plugs. 


Note  difference 
in  numbers  of 
spark  plugs  and 
distributor 
terminals 


Top  View 
FIG.  100. — High-voltage  Distributor. 

The  high-voltage  current  is  distributed  to  the  cylinders 
in  proper  order  by  the  rotation  of  the  distributing  arm  which 

w 


To  No.4  Spark  Plug 
•Distributing  Arm 

Induction  Coil  ,-Lorf  Vb/ftye 
/  Res&isfance 


Grounded  through  engine    ^--'Br  Breaker  shaft  gear  wheel 
and  frame  driven  at  one- ha  If  era  nk- 

Side    View  shaft  speed 

FlG.  101.— Side^View  of  Typical  Battery  Ignition  System. 

connects  by  means  of  sliding  contacts  the  central  high-voltage 
wire  W  from  the  induction  coil,  with  the  ends  of  the  wires 


AUTOMOBILE  IGNITION  123 

marked  1,  2,  4,  3  in  the  distributor  (Fig.  100),  carrying  the 
current  to  the  individual  spark  plugs.  The  number  of  wires 
in  the  distributor  head  with  which  the  distributing  arm  makes 
sliding  contact  is  the  same  as  the  number  of  engine  cylinders. 
The  figure  shows  also  the  movable  and  the  stationary  contacts 
used  to  "make"  and  "break"  the  battery  (low  voltage) 
current,  which  is  carried  from  the  induction  coil  to  the  sta- 
tionary contact  by  the  heavy  black  wire  shown  in  the  figure. 
The  moving  contact,  which  is  really  a  short  lever,  is  held 
in  its  normal  position  against  the  stationary  contact  by  a 
flat  spring.  At  the  side  of  the  contacts  there  is  a  small  cam 
which  has  as  many  lobes  or  teeth  as  there  are  engine  cylinders. 
This  cam  revolves  at  half  the  engine  speed  and  when  one 
of  its  lobes  is  opposite  the  moving  contact  the  lobe  pushes 
out  this  contact  so  as  to  separate  slightly  the  contacts  or 
breaker  points  and  thus  interrupts  the  battery  current  through 
the  induction  coil.  Every  time  the  contacts  or  breaker  points 
separate  there  is  an  induced  high-voltage  current  in  the  wind- 
ing of  fine  wire  of  this  induction  coil.  The  rotation  of  the 
cam  and  the  distributing  arm  must  be  so  timed  that  this 
induced  current  will  make  the  ignition  spark  in  each  engine 
cylinder  at  just  the  right  instant. 

Ignition  Safety  Resistance  Devices.  Nearly  all  modern 
ignition  systems  using  storage  batteries  have  a  safety  resistance 
coil  to  protect  the  battery  from  excessive  discharge  of  cur- 
rent in  case  the  ignition  switch  (shown  in  Fig.  101  over 
the  battery)  is  not  turned  off  when  the  engine  is  not  running 
and  the  breaker  points  are  in  the  position  of  contact.  This 
safety  coil  consists  of  a  number  of  turns  of  iron  alloy  wire 
which  has  the  property  of  increasing  its  resistance  as  it  is 
heated  by  electric  current ;  and  when  it  is  heated  to  a  cherry 
red  color  its  resistance  is  increased  enormously,  so  that  then 
very  little  current  can  go  through  the  coil  or  through  the 
rest  of  the  battery  circuit. 

Some  ignition  systems  have  a  device  for  releasing  auto- 
matically the  ignition  switch  on  the  dash  board  or  instrument 
board  if  it  is  left  on  unusually  long  when  the  engine  is  not 


124  GASOLINE  AUTOMOBILES 

running.  The  Connecticut  device  for  this  purpose  is  positive 
in  its  action  and  instead  of  reducing  the  flow  of  current 
to  a  safe  limit  as  with  a  safety  resistance  coil,  it  actually 
stops  the  flow.  The  essential  part  of  this  device  (Fig.  102) 
is  a  coil  of  high  resistance  wire  carrying  the  ignition  current, 
which  is  wound  around  a  flexible  rod  made  of  two  flat  strips 
of  spring  brass  and  nickel  steel  which  are  fastened  together 
at  the  ends.  When  the  ignition  current  heats  this  resistance 
coil  on  the  rod,  the  metal  strips  expand  unequally  as  the 
result  of  the  heating  and  the  rod  bends  toward  and,  if  the 
temperature  causes  sufficient  expansion,  touches  the  tip  of 
a  wire  contact  and  thus  makes  another  electric  circuit.  The 


Insulated 
Confacf 


Electro  Magnets 

FlG.  102.— Connecticut  Automatic 
Switch  Release. 

newly  formed  circuit  carries  current  to  an  electro-magnet 
which  has  enough  pulling  force  to  release  the  closed  ignition 
switch.  This  device  can  be  adjusted  to  operate  and  release 
the  ignition  switch  in  less  than  a  minute. 

In  some  battery  systems  a  safety  spark  gap  is  provided 
to  prevent  the  winding  of  fine  wire  on  the  induction  coil 
from  burning  out  in  case  a  spark  plug  wire  becomes  dis- 
connected, while  the  engine  is  running.  If  the  high-voltage 
circuit  is  disconnected  in  this  way  and  the  high-voltage 
current  cannot  complete  its  circuit  through  the  points  of  the 
spark  plug,  provision  is  made  so  that  the  current  can  dis- 
charge as  a  spark  in  the  air  gap  between  two  wires,  one 
of  which  is  connected  to  the  distributing  arm  of  the  dis- 
tributor and  another  is  grounded  to  the  breaker  shaft.  This 
safety  gap  should  not  be  set  for  a  shorter  distance  between 


AUTOMOBILE  IGNITION  125 

its  points  than  eleven  thirty-seconds  of  an  inch.  Otherwise 
the  high-voltage  current  may  jump  across  the  safety  spark 
gap  rather  than  across  the  air  gaps  of  the  spark  plugs  in 
the  cylinders.  If  this  occurs,  imperfect  ignition  will  result. 

Automatic  Spark  Advance.  In  a  battery  ignition  system 
the  amount  of  current  (amperes)  that  can  go  through  the 
various  resistances  does  not  depend  on  the  speed  of  the 
engine.  The  amount  of  current  is  practically  the  same 
whether  the  engine  speed  is  high  or  low.  At  low  engine 
speeds  there  are  few  ignitions  with  a  relatively  long  time 
between.  For  each  ignition  at  low  speed,  therefore,  a  strong, 
high-voltage  current  is  generated  in  the  coil  to  make  a 
"fat"  spark  at  the  spark  plugs  and  this  system  gives  excep- 
tionally good  ignition  sparks  for  starting  the  engine.  AVith 
these  good  conditions  at  low  speeds,  ignition  in  the  engine 
cylinders  is  almost  instantaneous.  At  high  engine  speeds, 
however,  battery  systems  can  have  little  time  for  generating 
the  high-voltage  current  for  ignition,  and  the  sparks  at  the 
spark  plugs  are.  weak  and  produce  slower  combustion.  In 
order,  therefore,  to  have  ignition  of  the  explosive  mixture 
in  the  cylinders  practically  complete  at  the  beginning  of 
each  explosion  stroke,  it  is  desirable,  when  battery  systems  are 
used,  to  advance  the  spark  automatically  by  some  mechanical 
means;  that  is,  to  make  the  spark  come  earlier  at  high  than 
at  low  speeds.  Otherwise  the  engine  will  waste  gasoline  and 
oil  and  will  be  easily  overheated. 

The  position  of  the  spark  as  to  advance  or  retard  can 
be  controlled  by  shifting  by  hand  the  spark  lever  on  the 
steering  wheel,  but  this  requires  the  constant  attention  of 
the  driver.  Provision  is  therefore  made  in  nearly  all  battery 
ignition  systems  for  the  automatic  advance  and  retard  of 
the  ignition  spark  by  the  use  of  revolving  governor  weights 
mounted  on  the  same  shaft  with  the  breaker  points  and  the 
distributing  arm.  A  commonly  used  method  is  to  fasten 
the  governor  weights  to  a  short  hollow  shaft  (Fig.  103)  which 
carries  also  the  distributing  arm  and  the  cam  for  moving 
the  breaker  points.  These  weights  move  toward  and 


126 


GASOLINE  AUTOMOBILES 


away  from  the  center  according  to  the  engine  speed.  This 
mechanism  is  arranged  so  that  as  the  engine  speed  increases 
the  weights  tend  to  move  outward  from  the  center  against 
the  resistance  of  springs,  and  the  cam  for  moving  the  breaker 
points  is  shifted  in  a  backward  direction  with  respect  to  the 
direction  of  motion  of  the  breaker  shaft.  This  has  the  effect 


Contact  Points 
Lever 


High  Voltage  W 
irom  Coll  to   Distributor 


m  Retaining  Screw 
for  Timing  Adjustment 


Spark  Adjust 
L 


Timer  Drive  Shaft 
Oil-Le.B  Bearings 
Spiral   Gear— 


Fl6.  103. — Sectional  Drawing  of  Distributor  and  Circuit 
Breaker  Device  of  Delco  Igniter. 


of  advancing  the  spark  automatically  to  the  correct  position 
required  for  the  engine  speed.  When  engine  speed  decreases, 
there  is  less  tendency  for  the  governor  weights  to  move 
outward  and  the  spring  pulls  them  inward  and  retards  the 
spark.  The  breaker  and  distributor  mechanism  together  with 
its  casing  is  sometimes  called  the  igniter. 


A  UTOMOBILE  IGNITION 


127 


Vibrating  Induction  Coil.  Fig.  104  shows  diagrammat- 
ically  an  induction  coil  of  the  vibrating  type  and  an  engine 
cylinder,  with  its  spark  plug.  This  type  of  coil  is  used  on 
Ford  automobiles.  The  iron  magnet  in  the  coil  is  marked 
M.  The  winding  of  heavy  wire  C  receives  the  low-voltage 
electric  current  from  the  battery  B,  which  produces  in  the 
winding  of  fine  wire  8  the  high  voltage  current  needed  for 
the  spark  plug  P.  In  the  operation  of  this  apparatus  the 
current  from  one  end  of  the  battery  B  goes  through  the  wire 
C  to  the  left-hand  end  of  the  device.  From  the  other  end 


High  Voltage  Circuit 


Fie.  104.— Vibrating  Ignition  Coil. 


of  the  battery  a  wire  goes  to  the  circuit  breaker  T,  and  from 
there  through  the  coil  to  the  base  of  vibrator  V.  To  complete 
the  circuit  the  current  goes  from  the  left-hand  end  of  battery 
to  the  screwholder  H,  through  the  screw  0,  down  the  flexible 
blade  of  the  vibrator  V,  and  then  to  the  right-hand  end  of 
the  low  voltage  winding  C.  At  the  upper  end  of  the  flexible 
vibrator  V  is  a  small  piece  of  soft  iron.  Now  in  the  operation 
of  this  device,  when  the  electric  current  goes  through  the 
winding  (7,  the  iron  bar  M  is  magnetized  and  causes  this  small 
piece  of  iron  on  the  vibrator  V  to  be  attracted  toward  it. 
This  magnetic  attraction  bends  the  flexible  blade  of  the 
vibrator  and  pulls  it  away  from  the  end  of  the  screw  O.  As 
soon  as  the  current  is  thus  broken  at  the  contact  points 


128  GASOLINE  AUTOMOBILES 

between  O  and  T,  the  iron  bar  M  loses  its  magnetism  and 
its  attraction  for  the  small  piece  of  iron,  so  that  the  flexible 
vibrator  V  returns  to  a  vertical  position.  When  the  vibrator 
is  vertical,  it  again  brings  together  the  contact  points  between 
O  and  V,  and  electric  current  once  more  flows  through  the 
winding  C  to  magnetize  the  iron  bar  M,  which  by  its  magnetic 
attraction  breaks  the  electric  circuit  as  before.  The  sequence 
is  repeated  with  great  rapidity  when  the  circuit  breaker  T 
is  in  the  position  so  that  the  cam  A  touches  the  metal  contact 
D  on  the  wire  connected  to  the  right-hand  end  of  the  coil. 
The  battery  current  does  not  go  to  the  spark  plugs  at  all. 
The  operating  principle  of  this  coil  and  its  vibrator  is  exactly 
the  same  as  that  of  an  ordinary  electric  door  bell. 

The  result  of  rapidly  opening  and  closing  the  contact 
points  between  the  screw  0  and  the  vibrator  V  is  to  make 
a  high-voltage  induced  current  in  the  high-voltage  winding 
8.  To  accomplish  this,  there  must  always  be  some  kind  of 
circuit  breaker  in  the  battery  circuit.  The  instant  the  points 
of  the  circuit  breaker  connect,  there  is  a  momentary  induced 
current  in  the  winding  8,  and  if  there  is  a  spark  plug  con- 
nected by  wires  to  this  winding,  the  induced  current  produces 
a  spark  at  the  "points"  of  the  spark  plug.  The  instant  the 
circuit  breaker  starts  the  battery  current  through  the  winding 
of  coarse  wire  C,  the  magnetism  due  to  this  current  goes 
through  the  winding  of  fine  wire  8,  and  induces  the  high 
voltage  current.  The  ends  of  the  winding  8  are  connected 
to  the  binding  posts  at  the  top.  Either  of  these  posts  may 
be  connected  by  a  wire  to  the  screw  cap  of  the  spark  plug  P 
in  the  engine  cylinder.  As  applied  to  an  automobile  engine, 
the  wire  from  the  other  post  is  usually  attached  securely  to 
the  engine  casting  or  frame  or  to  some  part  of  the  automobile 
in  metallic  contact  with  the  engine  cylinders.  A  wire  attached 
to  the  metal  of  the  engine  in  this  way  is  grounded.  The  high- 
voltage  electric  current  going  through  this  grounded  wire 
will  pass  through  the  metal  of  the  engine  to  the  body  of  the 
spark  plug  in  the  top  of  the  engine  cylinder.  Every  time 
the  contact  is  made  in  the  circuit  breaker  between  the  cam  A 


AUTOMOBILE  IGNITION 


129 


and  the  metal  contact  D,  a  spark  crosses  between  the  points 
of  the  spark  plug. 

Timers.  A  timer  is  a  mechanically  operated  circuit 
breaker  or  switch  intended  to  be  used  in  the  low-voltage 
circuit  of  an  induction  spark  coil.  For  example,  in  Fig.  105, 
the  timer  T  is  connected  in  the  circuit  of  the  low  voltage 
winding  C.  The  timer  shown  in  this  figure  is  for  an  engine 
with  four  cylinders,  so  that  there  is  a  coil  and  its  spark 
plug  connected  by  a  wire  to  each  of  the  timer  terminals. 
Each  of  these  terminals  is  in  metallic  contact  with  one 


FlG.  105. — Vibrating  Ignition  Coil  and 
Timor  (with  Condenser). 

of  the  metal  contact  blocks  Z),  set  in  the  inside  surface  of  the 
rim.  The  battery  B  has  one  terminal  connected  by  a  wire 
to  the  engine  casting  or  frame,  and  through  its  metal  and 
the  wires  shown  the  electric  current  goes  to  the  shaft  carrying 
the  roller  R  of  the  timer,  which,  by  its  rotation,  makes  electric 
contacts  with  the  blocks  D.  Briefly,  the  timer  is  a  device. for 
alternately  making  and  breaking  the  low-voltage  current,  thus 
distributing  the  induced  high-voltage  current  made  by  the 
vibrator  action  to  each  of  the  spark  plugs  in  the  engine 
cylinders  at  the  right  time. 

Hand-operated  Spark  Advance.     Attached  to  the   rim 
of  the  timer  is  an  arm  A  for  turning  the  rim  back  and  forth 


130  GASOLINE  AUTOMOBILES 

on  its  shaft.  If  the  rim  of  the  tinier  is  turned  in  the  direc- 
tion its  central  shaft  is  moving,  the  spark  will  occur  later  in 
the  stroke  of  each  of  the  engine  cylinders,  while  if  moved 
in  the  opposite  direction  the  spark  will  occur  earlier.  In 
the  former  case  the  spark  is  retarded  and  in  the  latter  it  is 
advanced.  On  practically  all  automobiles  this  arm  A  on  the 
rim  is  connected  by  a  rod  to  a  lever  on  the  steering  wheel, 
so  that  advancing  or  retarding  the  spark  is  under  the  control 
of  the  person  operating  the  automobile. 

Distributors  or  timers  for  six-,  eight-,  or  twelve-cylinder 
engines  are  similar  to  those  explained  except  that  they  have 
six,  eight,  or  twelve  terminals  in  the  rim  instead  of  four. 

Condensers.  In  the  operation  of  the  vibrator  V  of  a 
vibrating  induction  coil  (Fig.  105),  there  is  a  tendency  to  draw 
out  a  long  "  f at "  spark  at  the  contact  points  betwene  0  and  V 
every  time  the  current  is  stopped.  This  drawing  out  of  the 
spark,  if  not  prevented,  would  have  the  effect  of  wasting 
much  current,  weakening  the  spark  at  the  spark  plug  points, 
and  burning  off  the  contact  points  of  the  vibrator.  To  reduce 
these  ill  effects  a  condenser  shown  at  the  bottom  of  the  figure 
is  provided  as  part  of  a  complete  induction  or  spark  coil.  It  is 
connected  by  small  wires  "across"  the  air  gap  made  at  the 
contact  points  as  shown.  In  other  words,  one  terminal  of  the 
condenser  is  connected  to  the  low-voltage  wiring  on  one  side 
of  the  contact  points,  and  the  other  terminal  to  the  other  side. 
The  condenser  in  its  action  is  somewhat  like  a  shock  absorber 
on  the  body  of  an  automobile. 

Condenser  Construction.  A  condenser  consists  of  a 
number  of  sheets  of  tinfoil  separated  from  each  other  by 
sheets  of  oiled  paper.  Every  alternate  tinfoil  sheet  is  con- 
nected to  the  bottom  of  the  screw-holder  H  (Fig.  105),  the 
ends  of  the  other  tinfoil  sheets  are  connected  to  the  bottom 
of  the  vibrator  V.  If  a  condenser  is  attached  to  an  induction 
coil  of  any  kind  as  described  and  the  battery  current  going 
to  the  coil  is  stopped,  the  battery  current,  instead  of  following 
the  vibrator  points  and  making  a  long  spark,  spreads  over 
the  sheets  of  tinfoil  and  produces  a  charge  of  electricity  which 


AUTOMOBILE  IGNITION  131 

is  "stored "'to  be  given  back  to  the  circuit  when  these  contact 
points  again  come  together.  By  this  quick  and  clean  break- 
ing of  the  low-voltage  current,  an  induced  current  of  higher 
voltage  is  obtained  than  would  otherwise  be  the  case.  A 
condenser  increases  the  size  of  the  spark  about  twenty-five 
times.  Condensers  are  often  made  by  winding  together  two 
long  strips  of  tinfoil  separated  by  paraffine  paper. 

The  condenser  on  an  induction  coil  may  be  injured  if  the 
"points"  of  the  air  gap  of  a  spark  plug  are  too  far  apart. 
In  that  case  there  is  excessive  electric  stress  in  the  condenser 
which  causes  it  to  break  down.  If  the  condenser  is  defective 
and  there  are  large  sparks  at  the  vibrator,  there  will  be  weak 
sparks  at  the  spark  plugs,  but  weak  sparks  may  be  also  caused 
by  a  partial  breaking  down  of  the  condenser,  or  by  a  loose 
wire  at  the  condenser. 

Three-terminal  Induction  Spark  Coil.  Most  of  the 
vibrating  induction  coils  used  on  automobiles  have  only  three 
terminals  instead  of  the  four  terminals  in  Figs.  104  and  105. 
It  might  have  been  stated  in  the  description  of  the  coil  in 
Fig.  105  that  one  wire  from  the  high-voltage  winding  and 
one  wire  from  the  low-voltage  winding  are  grounded  to  the 
engine  casting.  These  two  wires  might  have  been  connected 
together  at  the  induction  coil  and  their  junction  connected 
through  the  timer  (grounded)  to  the  engine  casting  by  a 
single  wire  as  shown  in  Fig.  106.  In  a  three-terminal  coil  as 
made  for  commercial  use  one  end  of  the  low-voltage  winding 
is  joined  to  one  end  of  the  high-voltage  winding  and  the 
joining  place  of  these  two  windings  is  connected  directly  to 
one  of  the  binding  posts  marked  "common  ground — to  timer" 
as  shown  in  Fig.  107.  The  other  end  of  the  low-voltage  wind- 
ing is  connected  to  the  binding  post  marked  "battery,"  and 
the  other  end  of  the  high-voltage  winding  is  connected  to  the 
binding  post  marked  "plug"  (for  spark  plug).  Fig.  108 
shows  four  vibrating  spark  coils  similar  to  Fig.  107  as  they 
would  be  connected  to  the  timer  and  to  the  spark  plugs  of 
the  cylinders  of  a  Ford  engine.  The  four  separate  coils  for 
a  typical  four-cylinder  engine  are  packed  in  a  single  box 


132 


GASOLINE  AUTOMOBILES 


Ground*1 

FlG.  106.— Wiring  Diagram  of  Three 
Terminal  Vibrating  Coil. 


Adjusting  Nut  Vibnrtvr  Corrfack 


Condenser 


FIG.  107.— Three  Terminal  Vibrating 
Spark  Coil. 


AUTOMOBILE  IGNITION 


133 


similar  to  Fig.  109.     The  several  terminals  of  such  a  set  are 
usually  plainly  marked  on  the  sides  of  the  box. 

The  high-voltage  circuit,  as  shown  in  the  figures  is  from 
the  spark  plug  terminal,  across  its  air  gap  into  the  engine 


FlG.  108. — Vibrating  Spark  Coils  for  a 
Four-cylinder  Engine. 

casting  or  frame,  and  back  through  the  metal  of  the  engine 
to  the  grounded  side  of  the  high-voltage  winding. 

The  low-voltage  circuit  is  from  the  battery  to  the  low- 
voltage  winding  and  to  the  timer  where  the  wiring  is  grounded 


FIG.  108. — Vibrating  Spark  Coils  for  a 
Four-Cylinder  Engine. 

so  that  the  current  goes  back  to  the  battery  through  the  metal 
of  the  engine. 

Ford  Ignition  System.  In  the  Ford  system  of  ignition 
a  vibrating  spark  coil  similar  to  those  just  explained  is 
provided  for  each  cylinder  of  the  engine.  The  four  coils 
for  the  four  cylinders  of  a  Ford  engine  are  in  a  box  like 


134  GASOLINE  AUTOMOBILES 

Fig.  109,  usually  fastened  to  the  dash  board  or  instrument 
board  of  the  automobile.  Inside  the  box  there  is  a  strip 
of  brass  running  the  whole  length.  A  small  spring  on  the 
bottom  of  each  coil  makes  a  connection  on  this  brass  strip. 
This  spring  is  one  end  of  the  low-voltage  winding  of  each 
coil.  The  other  end  of  the  low-voltage  winding  of  each  coil 
comes  out  at  the  side  of  the  box  and  is  connected  to  one 
of  the  four  points  on  the  timer,  which  is  attached  to  the 
engine  behind  the  radiator  as  shown  in  Fig.  110.  The  timer 


No.l.Grttn - 

tlo.3  giue l- 

Ha£  Hid — -, 

HoJ  Black - 

BffraSturct  ofCurnnt 


Lamp  Wire  SraunJeJ-hffaJiirhr 
Wire 


FIG.  110. — Ignition  System  of  Ford  Automobile. 


sends  sparks  through  one  of  the  cylinders  for  each  quarter 
of  a  revolution.  It  has  a  rolling  contact  like  the  timer 
shown  in  Fig.  107  and  each  contact  bar  is  nearly  a  half  inch 
wide,  so  that  the  roller  stays  in  contact  longer  than  in  other 
circuit  breakers.  A  good  vibrator  on  such  a  coil  will 
make  two  hundred  sparks  a  second  and  when  starting  an 
engine  this  large  number  of  sparks  is  an  advantage.  More 
current,  however,  is  needed  for  a  "shower"  of  sparks  than 
for  a  single  spark,  and  when  the  engine  is  running,  such  a 
large  number  of  sparks  is  not  needed.  The  vibrator  should 
be  screwed  down  so  that  it  is  barely  touching.  It  is  best 
to  screw  it  down  slowly  until  the  cylinder  to  which  it  belongs 


AUTOMOBILE  IGNITION 


135 


begins  to  have  explosions.  Sometimes  the  points  on  the 
vibrator  must  be  smoothed  or  scraped  with  sand  paper.  If 
an  engine  misses  explosions  regularly  in  one  of  the  cylinders 
it  is  likely  one  of  the  spark  plugs  is  defective.  If,  however, 
the  engine  runs  irregularly  and  misses  an  explosion  only 
occasionally  with  sometimes  a  loud  noise  from  an  explosion 
in  the  muffler,  the  difficulty  can  often  be  remedied  by  adjust- 
ing the  vibrator  points. 

Master  Vibrators.     In  the  sets  of  vibrating  induction 
coils    described   in   the    preceding  Paragraphs   there   is    a 


FlG.  111. — Diagram  of  Wiring  of 
Master  Vibrator  Coil. 

separate  coil  for  each  engine  cylinder  so  that  when  the 
vibrators  on  the  coils  are  not  operating  properly,  each  coil 
must  be  separately  adjusted.  In  order  to  avoid  the  vibrator 
adjustments  on  a  number  of  coils  and  to  eliminate  the  pos- 
sibility of  getting  sparks  of  different  intensity  in  the  engine 
cylinders  a  master  vibrator  is  sometimes  used.  The  adjust- 
ment of  this  single  vibrator  serves  for  all  the  cylinders  of 
an  engine  and  when  it  is  installed  the  vibrators  on  the 
individual  coils  can  be  screwed  down  so  that  they  will  not 
operate.  When  a  master  vibrator  is  once  adjusted  all 
cylinders  will  get  ignition  sparks  of  practically  the  same 
intensity.  It  is  placed  in  a  spark  coil  system  between  the 
electric  battery  or  other  source  of  electric  current  and  the 


136 


GASOLINE  AUTOMOBILES 


low-voltage  windings  of  the  individual  spark  coils  as  shown 
diagrammatically  in  Figs.  Ill  and  112.  The  single  coarse 
wire  winding  of  the  master  vibrator  coil  and  the  wires  of  its 
vibrator  are  connected  in  series,  as  shown  in  the  figure,  with 
the  low-voltage  coils  of  each  of  the  individual  spark  coils. 


Ba-ffvry 
Ground  +o  Fngi'ne  Fn 

FIG.  112.— Master  Vibrator  Coil  for 
Ford  Engine. 

It  is  equally  necessary  to  provide  an  electric  condenser  to 
be  connected  across  the  contact  points  of  a  non-vibrating  coil 
ignition  system  as  to  provide  such  a  device  for  a  system  with 
a  vibrating  induction  coil.  Fig.  113  shows  the  same  induc- 


Plug 


Condenser 

FlG.  113. — Non-Vibrating  Induction  Coil 
with  Condenser. 

tion  coil  with  low-  and  high-voltage  wiring  as  in  Fig.  95  except 
that  a  condenser  is  used  to  "span"  the  circuit  breaker  points. 
This  condenser  has  the  effect,  as  explained  on  page  130,  of  pre- 
venting rapid  wearing  away  of  the  breaker  points  and  makes 
much  more  efficient  sparks  at  the  air  gaps  of  the  spark  plugs 
than  would  be  obtained  without  it.  Fig.  113  is  a  diagram- 


AUTOMOBILE  IGNITION 


137 


matic  representation  of  a  complete  non-vibrating  induction 
coil  as  applied  to  a  simple  type  of  battery  ignition  system. 
Fig.  114  is  similar  to  Figs.  100  and  101  as  to  the  essential 

1234 


From  Induction  Co//. 

Distributor  Head-. 


Stationary 
*•.  Contactflrtsu/crreJ) 
Grounded  Through  Engine  and  Automobile  Frame 
FIG.  114. — Typical  Battery  Ignition  System  with  Non- 
Vibrating  Coil  and  Condenser. 


Breaker 


Condenser 


ToSparlrfliys 


FIG.  115. — Ignition  System  with  Non-Vibrating  Coil  and 
Condenser  for  Six-Cylinder  Engine. 

parts,  except  that  it  has  a  condenser  which  is  located  on  the 
circular  bracket  supporting  the  contact  points  of  the  circuit 
breaker.  This  apparatus  is  for  a  four-cylinder  engine,  with 


138 


GASOLINE  AUTOMOBILES 


the  distributer  terminals  arranged  for  the  usual  timing  order 
1,  2,  4,  3  at  the  spark  plugs.  Fig.  115  shows  diagrammatically 
the  same  device  as  arranged  for  a  six  cylinder  engine. 

Typical  Non-vibrating  Coil  Ignition  Systems.  All  the 
electric  current  used  for  the  ignition,  the  lights,  and  the 
electric  horn  in  the  Delco  non-vibrating  coil  ignition  system 
shown  in  Fig.  116  goes  direct  from  the  storage  battery  to 
a  group  of  distributing  switches  on  the  dash  board  or  instru- 
ment board.  From  these  switches  the  current  is  distributed 


Dimming  Resistance 


To  Spark  Plugs 


Ground 


Insulated  Circuit 
greater  Contacts 
—  -Spring 


Ground  ', 

'•  Induction  Coil 
FIG.  116. — Wiring  Diagram  for  Typical  Delco  Ignition  System. 

for  the  three  services  as  stated.  When  the  engine  is  running 
and  is  driving  a  small  electric  generator  (not  shown  in  the 
figure),  which  is  a  part  of  this  system  the  current  comes 
through  the  wire  C  to  the  distributing  switch.  When  the 
storage  battery  is  supplying  the  current  it  comes  to  the  dis- 
tributing switch  through  the  wire  B. 

If  the  switch-button  for  the  ignition  circuit  is  pulled  out, 
the  electric  current  for  ignition  will  be  taken  from  either 
the  generator  or  from  the  storage  battery,  depending  on 
whether  or  not  the  engine  is  running  and  is  driving  the  electric 
generator. 


AUTOMOBILE  IGNITION  139 

When  the  electric  generator  is  giving  more  current  than 
is  needed  for  ignition,  lights,  etc.,  the  excess  of  current  goes 
through  the  wire  B  to  the  storage  battery  for  charging  it. 
An  ammeter  is  connected  to  this  wire  near  the  distributing 
switches  to  indicate  the  excess  current  which  is  going  into 
the  storage  battery  for  charging.  Automobiles  having  large 
lamps  in  the  headlights  will  sometimes  use  for  lighting  all 
the  current  the  generator  gives  when  the  automobile  is  run- 
ning at  average  speed,  and  no  current  is  left  for  charging. 
Such  automobiles  when  operated  much  at  night  and  little 
during  the  day  will  soon  have  very  little  ''charge"  in  the  , 
battery.  The  ammeter  is  also  connected  to  show  the  amount 
of  current  coming  from  the  storage  battery  for  lights  when 
the  engine  and  generator  are  not  running.* 

The  distributor  and  circuit  breaker  of  this  typical  system 
are  driven  by  gears  on  a  vertical  shaft  as  shown  in  Fig.  103. 
The  distributor  consists  of  a  cap  of  insulating  fiber  which 
has  one  high-voltage  contact  in  the  center  connected  by  a 
wire  to  the  non-vibrating  induction  coil  and  as  many  similar 
contacts  spaced  equidistant  about  the  center  as  there  are  spark 
plugs  in  the  engine.  The  circuit  breaker  is  below  the  dis- 
tributor and  gets  its  motion  from  the  same  vertical  shaft 
that  drives  the  distributing  arm.  It  has  a  screw  at  the  center 
of  the  shaft,  which  when  unscrewed  permits  turning  the  cir- 
cuit breaker  cam  to  adjust  the  timing  of  the  spark  in  the 
cylinders.  Turning  it  clockwise  advances  the  spark,  and 
turning  it  anti-clockwise  retards.  The  spark  is  made  in 
the  cylinders  at  the  instant  the  breaker  contacts  are  separated. 

The  non-vibrating  induction  coil  is  provided  for  transform- 
ing (by  the  usual  method  already  explained)  the  low  voltage 
(about  five  to  seven  volts  for  three  cells)  to  the  high  voltage 
of  about  10,000  volts  needed  for  spark-plug  ignition.  It  con- 
sists simply  of  a  low-voltage  winding  of  relatively  few  turns 
of  coarse  wire  wound  around  a  central  core  of  iron  rods,  and 


*The  ammeter  does  not  show  current  used  by  the  electric  motor  for 
starting  the  engine. 


140 


GASOLINE  AUTOMOBILES 


a  high-voltage  coil  of  many  turns  of  fine  wire  wound  over  the 
coarse  wire  coil. 

At  high  speed  the  spark  should  be  advanced  farther  than 
at  low.     In  ignition  systems  with  automatic  spark  control 


FIG.  117. — Delco  Igniter  with 
Vertical  Coil. 


Storage  &#ery       Imrht'on  Snitch 
12-Wfs  } 


«*.»%r    ..    V  cL^*""1'-       •'*"***• 

Wndm&Seyeral .   .    LowVoltage  Winding, 
Thousand  Turns        A  Few  Hundred  Tirme. 

FIG.  118.— Delco  Ignition  System  with  Horizontal  Coil. 

it  is  usually  unnecessary  to  make  adjustments  of  the  hand 
spark  lever  for  speed  changes  after  the  engine  is  started  and 
is  running  normally. 

Special  types  of  the  Delco  ignition  system  are  shown  in 
Figs.  117  and  118.     In  the  first  of  these  figures  the  high- 


AUTOMOBILE  IGNITION 


141 


voltage  wire  going  from  the  induction  or  ''ignition"  coil  to 
the  distributor  is  marked  W3.     The  connections  to  the  ter- 

Ignifion  and  Lighting  Snitch 
—I  Ground 


Safety  Spark  Gap 
FIG.  119. — North  East  Battery  Ignition  System. 

minals  of  the  low-voltage  winding  on  the  coil  are  marked 
W\  and  W2. 


Distributor  Brush \ 
Distributor  Arm  \ 


Circuit  Breaker^ 
Arm 


LowYolfage 

Coil 
Terminals 


v  Wires  to  Spark  Plugs 
Distributor  Head 

Cocrpfmj 


High  Voltage  Coil  Terminal v 


/_ ,  Spiral  Gears 
- -Automatic  Spark 
Advance  Weights 
FIG.  120. — Igniter  of  North  East  Ignition  System. 


North  East  Battery  Ignition  System  is  used  on  many 
Dodge  Automobiles.  One  of  the  differences  when  compared 
with  the  typical  system  described  is  that  it  has  always  a 


142 


GASOLINE  AUTOMOBILES 


twelve-volt  storage  battery  instead  of  the  more  usual  six-volt 
battery.  Fig.  119  shows  a  diagram  of  the  wiring  for  this 
system.  There  is  a  safety  spark  gap  for  the  protection  of  the 
high-voltage  winding  on  the  induction  coil.  As  actually  con- 


FIG.  121.— Automatic  Spark  Advance  Weights 
(North  East  System). 

structed  the  ignition  coil  and  distributor  head  are  arranged 
as  shown  in  Fig.  120.  Automatic  spark  advance  weights  are 
located  at  the  end  of  the  horizontal  drive  shaft.  These  weights 
are  shown  more  in  detail  in  Fig.  121.  They  operate  by  the 


FIG.  122.— Circuit  Breaker  of  North  East  Ignition 
System  Showing  Condenser. 

usual  centrifugal  method.  A  detail  of  the  circuit  breaker  is 
shown  in  Fig.  122,  which  shows  also  the  location  of  the  con- 
denser and  its  connecting  wires  W\  and  W2  as  joined  to  the 
two  contact  points  A  and  B.  The  low-voltage  terminals  are 
marked  T  and  U. 


AUTOMOBILE  IGNITION 


143 


Connecticut  Ignition  System  is  shown  in  a  perspective 
drawing  in  Fig.  123.  A  detail  of  the  circuit  breaker  mechan- 
ism is  shown  at  the  left-hand  side  of  the  drawing.  At  the 


Storage  Battery 

FIG.  123. — Connecticut  Ignition  System. 

right-hand  side  is  a  small  drawing  with  parts  marked  K,  L, 
T,  of  the  Connecticut  Automatic  switch  release  which  was 
explained  on  page  124.  The  drawing  shows  the  electric  cur- 


*•  To  Spark  Plugs 


^Distributor  Brushes 


FIG.  124. — Diagram  of  Westinghouse  Igniter. 

rent  for  ignition  taken  either  from  a  storage  battery  or  from 
a  small  electric  generator. 

Westinghouse  Ignition  system  is  shown  here  merely  with 
details  of  the  distributor  and  the  circuit  breaker.     The  usual 


144 


GASOLINE  AUTOMOBILES 


arrangement  of  the  distributor  over  the  circuit  breaker  is 
shown  diagrammatically  in  Fig.  124.  A  phantom  view  of  the 
igniter  shown  in  Fig.  125  shows  the  method  of  making 


FIG.  125. 
Westinghouse   Igniter. 

contact  between  the  distributing  arm  and  the  spark  plug  ter- 
minals on  the  distributor.    This  system  is  described  more  in 


FIG.  126. — Atwater-Kent  Battery  Ignition  System. 

detail  in  the  explanation  of  the  Westinghouse  starting  and 
lighting  system  on  pages  180-182. 

Atwater-Kent  Ignition  System  is  shown  by  the  diagram 
in  Fig.  126.     The  principal  difference  between  this  system 


AUTOMOBILE  IGNITION 


145 


and  most   others  is   that   the  contact   points  of  the  circuit 
breaker  are  together  and  touching  only  for  an  instant  just 


Fie.  127. — Detail  of  Distributer  Arm  of 
Atwater-Kent  System. 


FIG.  128. — Detail  of  Attachment  of  High  Voltage 
Wires  to  Distributer  Head. 


Mechanism          DryCt 

FiQ.  129. — Kemy  Ignition  System. 


preceding  the  moment  when  the  spark  is  to  be  made  in  one 
of  the  engine  cylinders.     Because  of  this  arrangement  it  is 


146 


GASOLINE  AUTOMOBILES 


High  Voltage  Cable 
from  Coll 


Leads  for  Attachment  of 
'Wires  to  Plugs 


Distributor  Cover 


Spark  Adjustment  Lerer 
Drive  Shaft 


Ground  Ground1 

FlS.  130.— Igniter  of  Kemy  Battery 
Ignition  System. 


FIG.  131. 
Eemy  Igniter. 


FIG.  132. 
Bosch  Igniter. 


AUTOMOBILE  IGNITION  147 

unnecessary  to  have  a  protective  device  to  guard  against  over- 
heating in  case  the  ignition  switch  should  be  left  closed  when 
the  engine  is  not  running.  Details  of  the  distributing  arm 
and  method  of  attachment  of  the  high-voltage  wires  to  the 
distributor  terminals  are  shown  in  Figs.  127  and  128. 

Remy  Ignition  System  is  shown  clearly  in  Figs.  129  and 
130.  As  shown  in  the  latter  figure  the  igniter  (distributor 
and  circuit  breaker)  is  mounted  on  a  bracket  which  also  sup- 
ports the  induction  coil.  Another  view  is  shown  in  Fig.  131. 

The  igniter  used  in  the  new  Bosch  battery  system  is  shown 
in  Fig.  132. 


CHAPTER   VI 
MAGNETOS  AND  IGNITION  TESTING 

In  the  preceding  paragraphs  the  elementary  principles 
of  the  relation  of  electricity  to  magnetism  were  explained. 
Typical  applications  were  illustrated  in  devices  intended  for 
the  ignition  of  explosive  mixtures  of  gasoline  vapor  and  air 
in  automobile  engines.  The  applications  of  these  principles 
will  now  be  extended  to  generating  electric  current  for  igni- 
tion purposes  without  the  use  of  batteries  of  dry  or  storage 
cells.  Electric  generators  for  such  ignition  purposes  are  called 
magnetos.  A  magneto  as  regards  the  essential  parts  is  an 
ignition  system  in  itself.  Magneto  ignition  systems  are  not 
used  as  much  as  formerly  on  modern  pleasure  automobiles. 

When  a  wire  loop  like  L  in  Fig.  94  is  moved  in  a  magnetic 
field  an  electric  current  is  generated  in  the  wire.  Consider 
now  Fig.  133  which  shows  a  bent  bar  magnet  and  a  wire  loop 
placed  between  the  ends  of  the  magnet.  If  the  loop  is  re- 
volved in  the  position  shown  an  electric  current  will  be  gen- 
erated. Electrical  pressure  or  voltage  is  generated  in  the 
loop  in  proportion  to  the  speed  of  its  rotation — the  faster  the 
loop  is  revolved,  the  higher  the  voltage  produced.  By  increas- 
ing the  number  of  loops  and  the  strength  of  the  magnetic 
field  of  the  magneto  the  amount  of  current  (amperes)  is 
increased. 

These  are  the  fundamental  principles  of  the  dynamo,  in- 
cluding the  electric  generator  and  the  automobile  magneto. 
A  double  wire  loop  in  position  for  revolving  in  the  magnetic 
field  of  a  typical  magneto  is  shown  in  Fig.  134.  At  the  bottom 
of  this  figure  is  another  double  coil  wound  on  a  shuttle- 
shaped  iron  core  for  holding  the  wire  loops.  The  iron  core 
and  its  windings  are  called  the  armature  of  the  magneto. 
148 


MAGNETOS  149 

The  magnetic  fields  of  all  kinds  of  magnetos  are  made 
of  permanent  magnets,*  which  remain  magnetized  indefi- 
nitely. Magnetos  should  always  be  positively  driven  by  gear 
wheels  from  the  engine  shaft  because  the  timing  of  the  spark  is 


FIG.  133. — Bent  Bar  Magnet  and  Wire  Loop. 

determined  by  the  timer  which  is  a  part  of  the  mechanism  of 
the  magneto.  A  belt-driven  magneto  would  not  give  accurate 
timing  of  the  spark. 

Magneto  Armature  Types.    The  armature  of  a  magneto 


FIG.  134. — Magneto  Coils. 

consists  of  an  iron  frame  and  the  wire  coils  in  which  the 
electric  current  is  generated  for  ignition.    A  magneto  arma- 


*  If  a  permanent  magnet  is  used  for  making  the  magnetic  field  the 
machine  is  called  a  magneto;  and  if  electromagnets  are  used  the  machine 
is  called  an  electric  generator. 


150 


GASOLINE  AUTOMOBILES 


ture  is  not  necessarily  a  moving  part;  although  in  most 
designs  it  is  of  the  rotating  kind  similar  to  the  one  shown 
in  Fig.  134.  There  is  another  kind  in  which  the  coils  of  wire 


FIG.  135. — Magneto  with  Stationary 
Wires   (Armature). 

generating  the  ignition  current  are  stationary  and  the  rotating 
part  consists  only  of  iron  without  a  winding.  In  the  latter 
kind,  by  generating  the  electric  current  in  stationary  coils 
the  usual  sliding  contacts  on  current  collecting  rings  are 
avoided.  (See  Figs.  135  and  136.) 


FIG.  136. — Magneto  Rotor  without  Wires. 

Magneto  Speed  Compared  to  Engine  Speed.  Modern 
types  of  magnetos  make  two  sparks  in  one  revolution  of  the 
magneto  shaft.  A  four-cylinder  automobile  engine,  for 
example,  has  four  explosion  or  power  strokes  in  two  revolu- 
tions, so  that  the  magneto  for  this  engine  must  make  four 
sparks  in  every  two  revolutions  of  the  engine,  or  two  sparks 
in  every  revolution.  In  a  four-cylinder  engine,  therefore,  the 
magneto  shaft  and  the  engine  crank  shaft  must  rotate  at  the 
same  speed.  In  a  six-cylinder  automobile  engine  there  are 
three  explosions  in  one  revolution  of  the  engine  crank  shaft, 
and  in  an  eight-cylinder  engine  there  are  four  explosions. 
The  speed  of  the  magneto  shaft  of  six-  and  eight-cylinder 
engines  must  be,  therefore,  respectively  one  and  a  half  and 
two  times  the  speed  of  the  crank  shaft. 


MAGNETOS  151 

Kinds  of  Magnetos.  There  are  two  kinds  of  magnetos: 
(1)  high  tension,  meaning  high  voltage  and  (2)  low  tension, 
meaning  low  voltage.  A  high-tension  magneto  has  two  wind- 
ings or  coils  on  its  iron  core ;  one  coil  consists  of  a  few  turns 
of  coarse  wire,  like  the  low-voltage  coil  in  an  induction  coil 
and  another  consists  of  a  large  number  of  turns  of  very  fine 
wire  wound  over  the  low-voltage  coil.  High-tension  magnetos 
are  used  much  more  than  the  low-tension  type  for  automobile 
ignition. 

A  low-tension  magneto  differs  from  a  high-tension  in  hav- 
ing only  one  winding  of  wire  on  the  armature.  It  delivers 
only  low-voltage  current  at  its  terminals  and  a  voltage  trans- 
former* must  be  used  to  step-up  the  magneto  voltage  to  make 
its  current  suitable  for  spark-plug  ignition.  Sometimes  a 
transformer  is  set  on  top  of  the  magneto  and  this  combination 
is  sometimes  called  a  high-tension  magneto  but  it  should  not 
be  given  that  name,  as  it  does  not  give  the  kind  of  service 
expected  of  a  real  high-tension  magneto. 

High-tension  Magneto.  The  essential  parts  of  a  high- 
tension  magneto  (with  the  magnets  omitted)  are  shown  in 

Spark 
Plugs 


Ground 

FIG.  137. — Diagrammatic  View  of 
Parts   of  Magneto. 

Fig.  137.  The  low-voltage  coil  on  the  armature  A  is  repre- 
sented by  heavy  lines  and  the  high-voltage  coil  by  light  lines. 
The  high-voltage  and  the  low-voltage  coils  are  connected  at  X 


*  A  voltage  transformer  or  what  is  commonly  called  an  electric  trans- 
former consists  of  two  coils  of  wire  wound  upon  each  other,  one  of  few 
turns  of  coarse  wire  for  the  low-voltage  current  and  the  other  of  many 
turns  of  fine  wire  for  the  high  voltage. 


152  GASOLINE  AUTOMOBILES 

and  from  this  point  a  wire  a  is  "grounded"  to  the  metal  frame 
of  the  magneto.  In  this  diagrammatic  representation  a  circuit 
breaker  is  shown  at  the  left-hand  end  of  the  armature  which 
is  generally  operated  by  some  kind  of  cam  device  to  break 
the  current  twice  in  a  revolution.  This  circuit  breaker  con- 
sists of  a  pivoted  lever  L  which  has  a  platinum  point  E  at 
one  end  and  a  fiber  block  C  at  the  other  end.  Normally,  the 
platinum  point  E  is  held  by  a  spring  against  the  point  F 
on  the  insulated  block  D,  which  is  connected  to  the  low-voltage 
winding  on  the  armature.  As  a  magneto  is  actually  con- 
structed, the  pivoted  lever  L  and  the  insulated  block  D  are 
mounted  on  the  end  of  the  armature  shaft  8,  and  in  their 
rotation  with  the  armature  the  piece  of  fiber  C  on  the  lever 
L  passes  over  the  stationary  cams  Ct  and  Cz  (Fig.  138)  and 


FIG.  138. — Typical  Magneto 
Circuit  Breaker. 


swings  the  lever  L  back  and  forth  to  break  the  circuit  by  the 
separation  of  the  points  E  and  F. 

At  the  right-hand  end  of  the  armature  shaft  is  a  copper 
collector  ring  R  (Fig.  137), insulated  from  the  shaft  by  a  band 
of  hard  rubber.  By  means  of  this  ring  the  high-voltage  cur- 
rent generated  in  the  armature  of  the  magneto  is  collected  by 
a  carbon  brush  B,  which  is  held  down  to  make  electrical 
contact  on  the  collector  ring  R  by  the  spring  K.  This  col- 
lector ring  is  connected  to  the  free  end  of  the  high-voltage 
coil  on  the  armature  so  that  the  current  from  this  coil  passes 
to  the  ring  R,  and  from  there  through  the  carbon  brush  B 
and  the  wire  W  to  the  distributing  arm  which  distributes  the 
high-voltage  current  to  the  spark  plugs  in  the  proper  order 


MAGNETOS 


153 


of  firing.  The  timing  arm  T  and  its  attached  cams  C^  and  C2 
are  fastened  to  a  ring  r  which  is  mounted  on  the  magneto 
frame  so  as  to  permit  a  little  back  and  forth  movement.  The 
timing  arm  is  therefore  a  means  of  moving  the  cams  slightly 
so  as  to  cause  the  sparks  at  the  spark  plugs  a  little  earlier  or 
later  than  for  the  setting  shown.  This  arm  is  fitted  with 
attachments  for  connection  to  the  spark  control  lever  on  the 
steering  wheel. 

A  "phantom"  view  of  a  typical  high-tension  magneto  is 
shown  in  Fig  139.     The  current  from  the  high-voltage  wind- 


flag  nets.. 


Co/lector  Brush-"?) 


Collector  Ring 
•  R 


Circuit  Breaker 
Mechanism 


Low  Voltage  Winding          '"  High  Voltage  Winding 

FIG.  139. — Phantom  View  of  High-tension  Magneto  for  a  Four-Cylinder 
Engine.  (Note  only  two  of  the  four  spark  plug  terminals  are 
shown.) 

ing  is  carried  by  a  wire  passing  through  the  right-hand  end 
plate  to  the  collector  ring  R,  from  which  the  current  passes 
througji  the  collector  brush  B  and  the  wire  W  to  the  dis- 
tributing arm  at  the  left-hand  end  of  the  magneto.  The 
distributing  arm  is  driven  by  the  gear  wheels  as  shown  at 
one-half  the  speed  of  the  armature  shaft  on  a  four-cylinder 
engine ;  and  at  one-third  the  armature  speed  on  a  six-cylinder 
engine. 

Two  sparks  are  made  by  a  magneto  in  every  revolution 


154 


GASOLINE  AUTOMOBILES 


of  this  armature  so  that  the  armature  of  a  magneto  for  a 
four-cylinder  engine  must  make  two  revolutions,  causing  four 
sparks,  in  the  same  time  that  the  distributor  brush  makes  one 
revolution.  The  gears  are  so  arranged  that  when  each  of 
the  sparks  is  produced  the  distributing  arm  is  resting  on  the 
bar  or  segment  connected  to  the  proper  spark  plug. 

A  condenser  for  shortening  the  duration  of  the  spark  at 
the  contact  points  E  and  F  (Fig.  137)  in  the  low- voltage 
circuit  is  mounted  at  the  end  of  the  armature  shaft.  As  the 
diagram  in  Fig.  137  is  laid  out,  one  terminal  of  the  con- 
denser would  be  connected  at  X  and  the  other  to  the  wire 


Cotrfnct-Bngoker 


FIG.  140. — Magneto  with  Condenser  on  Armature  Shaft. 


shown  dotted  through  the  hollow  shaft  8.  Figs.  140  and  141 
show  the  condenser  as  located  in  a  magneto  of  a  well-known 
make. 

A  diagram  of  a  high-tension  magneto  of  the  Bosch  make  for 
a  four-cylinder  engine  is  shown  in  Fig.  142,  with  the  impor- 
tant parts  marked  with  numbers  which  are  explained  in  the 
table  below  the  figure.  A  somewhat  simpler  design  is  shown 
in  Fig.  143. 

Safety  Spark  Gap.  If  by  accident  the  wire  connecting 
the  high-voltage  coil  of  the  armature  to  the  collector  ring  R 
(Fig.  137)  is  broken  or  detached,  the  high -voltage  current 
will  have  no  return  path  and  may  produce  a  voltage  which 
will  damage  the  insulation  of  the  high  voltage  coil  on  the 
armature.  Similar  damage  may  result  from  the  excessive 


MAGNETOS 


155 


voltage  if  the  platinum  points  E  and  F  of  the  circuit  breaker 
are  too  far  apart  or  if  a  wire  falls  off  one  of  the  spark  plugs 


when  the  engine  is  running  so  that  the  electric  current  cannot 
go   through   the  plug.     To   protect   the  high-voltage   coil   a 


156 


GASOLINE  A  UTOMOBILES 


safety  spark  gap  is  provided  as  shown  at  the  left-hand  side 
of  Fig.  141.    One  side  is  connected  to  the  collector  brush  and 


FlG.  142. — Typical  High-tension  Magneto. 


E.  Collector  ring. 
B.  Carbon  brush. 

12.  Brush  holder. 

13.  Terminal  piece  for  bar  14. 

14.  Conducting  bar. 

15.  Distributor  brush  holder. 


Z    L    K 


16.  Distributor  carbon  brush. 

17.  Distributor  cover. 

18.  Central  distributor  contact-. 
20.  Nut  on  distributor. 

22.  Dust  cover. 
170.  Nut  on  grounding  terminal. 


H    V    N    L 


FiO.  143. — Simplified  Type  of  High-tension  Magneto, 
the  other  is  attached  ("grounded")  to  the  frame  of  the  mag- 


MAGNETOS  157 

neto.  The  current  will  pass  through  this  air  gap  in  case 
the  high-voltage  line  is  incomplete. 

The  discharge  through  this  spark  gap  should  not  be  al- 
lowed to  continue  for  a  long  time  as  it  is  likely  to  damage 
the  magneto.  One  way  of  locking  an  automobile  is  to  put 
a  little  piece  of  metal  between  the  points  of  the  safety  spark 
gap.  The  engine  can  then  be  "cranked"  indefinitely  without 
making  a  spark  in  any  of  the  cylinders. 

If  this  description  of  a  typical  high-tension  magneto  is 
understood,  the  reader  should  have  little  difficulty  in  under- 
standing the  construction  of  any  other  magneto  of  similar 
design. 

Ford  Low-tension  Magneto.  The  Ford  magneto  is  in 
the  same  case  or  housing  which  covers  the  speed-change 


Copper  Wire- 


Magneto  Coil--'' 
Spool 


'Magnet  Clamp 
FIG.  144. — Essential  Parts  of  Ford  Low-tension  Magneto. 

gears  or  transmission.  Fig.  144  shows  the  important  parts 
consisting  of  sixteen  small  coils  of  wire  in  a  stationary 
round  plate  and  sixteen  magnets.  Each  coil  has  an  iron 
core  and  the  winding  of  wire  around  these  cores  is  continuous. 
The  stationary  plate  and  the  flywheel  have  about  the  same 
diameter.  There  are  sixteen  magnets  shaped  like  horseshoes 


158 


GASOLINE  AUTOMOBILES 


on  the  flywheel  and  the  space  between  these  magnets  and  the 
coils  on  the  stationary  plate  is  only  about  a  thirty-second 
of  an  inch. 

The    magnets    on   the   flywheel   set   up    a   magnetic    field 
which  when  rotating  in  front  of  the  coils  on  the  stationary 


'•••Flywheel  Miynefc 

FIG.   145.— Ford   Flywheel   Magneto   and 
Vibrating  Induction  Coils. 

plate  generate  an  electric  current  in  these  coils.  The  magneto, 
timer,  and  vibrator  spark  coils  are  shown  diagrammatically 
in  Fig.  145.  Fig.  146  is  a  drawing  of  a  Ford  engine  showing 
the  flywheel  magneto. 

Graphite  should  not  be  put  in  the  oil  used  in  a  Ford 
engine  as  it  is  likely  to  injure  the  coils.  Sometimes  the 
magnets  become  demagnetized,  causing  weak  ignition  sparks. 
In  that  case  the  magnets  should  be  replaced  with  new  ones. 
A  Ford  magneto  has  only  one  winding  which  generates  a 
low-voltage  current  of  about  18  volts,  when  the  engine  is 
running  at  normal  speed. 

Dual  and  Double  Ignition  Systems.  Since  the  amount 
of  current  and  voltage  generated  by  a  magneto  depends 
on  its  speed,  it  is  obvious  that  at  the  low  speed  of  starting, 
especially  of  hand  cranking,  it  is  often  difficult  to  get  good 
electric  sparks  in  the  engine  cylinders  for  ignition.  For  this 
reason  some  automobiles  are  provided  with  some  other  source 
of  current  for  start-ing.  The  auxiliary  source  is  a  battery 
of  dry  cells  or  of  storage  cells.  In  the  dual  system  of  igni-' 
tion  the  battery  supplies  the  current  for  starting,  which  is 


MAGNETOS 


159 


taken  through  a  separate  circuit  breaker  and  then  through 
the  low-voltage  winding  on  the  armature  of  the  high-ten- 
sion magneto.  The  high-voltage  current  is  then  generated  as 


in  a  non-vibrating  induction  coil  and  goes  from  the  magneto 
distributor  to  the  spark  plugs.  After  the  engine  is  started, 
by  the  movement  of  a  switch,  the  magneto  current  can  be 


160  GASOLINE  AUTOMOBILES 

used  for  engine  ignition  in  the  ordinary  way.  Some  induction 
coils  are  provided  with  a  ratchet  device  on  the  dash  board 
which  makes  a  "shower"  of  sparks  for  starting  by  rapidly 
making  and  breaking  the  ignition  circuit. 

In  the  double  system  of  ignition  the  engine  has  two  spark 
plugs  in  each  cylinder,  one  of  which  gets  current  from  a 
battery  and  induction  coils  and  the  other  from  the  magneto. 
In  this  system  there  are  really  two  separate  ignition  outfits, 
and  the  engine  can  be  operated  on  either  one  or  both  at  any 
time. 

Care  of  Magnetos.  If  any  moisture  gets  on  the  high- 
voltage  coil  of  a  magneto  it  may  cause  a  short  circuit  so 
that  the  high-voltage  current  will  not  go  to  the  spark  plugs 
but  will  go  through  the  insulation  of  the  coil  and  conse- 
quently the  engine  will  be  stopped. 

The  bearings  on  each  end  of  the  magneto  shaft  should 
occasionally  have  a  few  drops  of  oil.  But  this  is  one  part 
of  an  automobile  that  should  not  be  oiled  too  much.  As 
regards  any  other  part  of  an  automobile  it  is  best  to  give 
too  much  oil  rather  than  too  little.  A  magneto  should  be 
kept  clean  and  dry.  Repairing  a  magneto  is  work  for  an 
expert  electrical  mechanic  and  should  not  be  attempted  by 
amateurs. 

Magneto  Adjustments.  Timing.  If  a  magneto  is  out  of 
adjustment,  the  engine  should  be  cranked  until  "No.  1" 
cylinder  (the  one  nearest  the  radiator)  is  in  the  position 
of  firing  the  explosive  mixture.  This  is  usually  just  a  little 
past  the  dead  center  (top  of  stroke)  if  the  spark  is  set 
for  the  usual  starting  position  (not  advanced).  Next 
determine  which  one  of  the  distributor  points  is  wired  to 
"No.  1"  cylinder.  Then  rotate  the  armature  of  the  magneto 
until  the  distributing  arm  comes  into  contact  with  the 
distributing  points  for  "No.  1"  cylinder,,  and  adjust  these 
relative  positions  so  that  the  contact  points  are  released  from 
each  other  when  the  distributing  ring  is  in  the  position  of 
a  fully  retarded  spark.  In  this  position  the  magneto  should 
be  carefully  attached  to  its  driving  shaft.  The  spark  con- 


MAGNETOS  161 

trol  rod  going  to  the  steering  wheel  should  then  be  con- 
nected and  adjusted  so  that  the  contact  points  just  open 
when  the  spark  lever  on  the  steering  wheel  is  fully  retarded. 
This  position  of  the  lever  permits  advancing  the  ignition 
spark  the  maximum  amount.  The  circuit  breaker  points 
of  a  magneto  are  opened  about  one-sixty-fourth  of  an  inch, 
while  on  a  battery  system  they  are  usually  opened  about  twice 
as  much.  A  gage  is  usually  furnished  for  setting  the  circuit 
breaker  points  of  a  magneto.  The  carbon  brushes  of  the 
distributor  will  collect  dust  and  should  be  occasionally  cleaned 
with  a  piece  of  clean  cloth. 

Demagnetized  Magnets.  If  the  magnets  are  weak  the 
sparks  will  be  weak.  The  spark  depends  not  only  on  the 
strength  of  the  magnets  but  also  on  the  speed  of  the  engine. 
Increased  engine  speed  gives  better  ignition  current  from 
a  magneto  with  weak  magnets. 

If  an  engine  stalls  easily  when  driving  through  crowded 
city  streets  and  seems  to  have  little  power  at  slow  speeds 
it  is  likely  that  the  magnets  are  weak  and  the  ignition 
current  is  of  very  low  voltage.  The  magnets  can  be  remag- 
netized  in  a  very  short  time  and  without  much  expense. 

Magneto  vs.  Battery.  A  magneto  gives  a  very  hot  spark 
at  high  speed.  Magnetos  are  used  more  on  trucks  than  on 
automobiles.  Most  modern  automobiles  have  an  electric  self- 
starter  and  a  storage  battery  system,  so  arranged  that  one  can 
get  into  the  seat  and  start  without  cranking  the  engine.  A 
battery  ignition  system  gives  a  hotter  spark  at  low  speed  than 
a  magneto  system.  But  when  running  at  high  speed  a  mag- 
neto may  give  a  hotter  spark  than  a  battery. 

There  is  much  advertising  of  the  merits  of  one  of  these 
systems  of  ignition  over  the  other.  The  double  system  of 
ignition  shows  both  methods  under  the  same  conditions. 
Careful  experiments  show  that  there  is  practically  no  differ- 
ence as  to  the  effectiveness  of  the  two  methods  of  ignition. 

Testing  Spark  Plugs.  When  a  spark  plug  has  been  taken 
out  for  cleaning,  it  should  be  screwed  back  again  into  the 
cylinder  tightly  so  that  there  will  be  no  loss  of  compression 


162  GASOLINE  AUTOMOBILES 

pressure  by  leakage  and  it  should  be  put  back  carefully 
to  avoid  changing  of  the  air  gap  distance  or  breaking  the 
porcelain.  It  is  a  good  precaution  to  take  out  the  spark 
plugs  and  clean  them  before  going  on  a  long  trip.  If,  after 
cleaning  a  spark  plug,  the  ignition  in  the  cylinder  in  which 
it  belongs  is  still  not  as  it  should  be,  the  spark  plug  should 
be  put  into  another  cylinder  and  if  there  is  then  difficulty 
with  the  ignition  in  that  cylinder,  it  may  be  assumed  the 
spark  plug  is  defective. 

The  easiest  way  to  tell  whether  any  of  the  cylinders 
of  an  engine  are  not  working  is  to  test  each  of  the  spark 
plugs  by  putting  the  end  of  a  screw-driver  with  a  wooden 
handle  on  the  casting  or  frame  of  the  engine  and  touching 
the  side  of  its  steel  blade  on  the  metal  top  of  the  spark 
plug.  The  current  will  then  go  from  the  top  of  the  spark 
plug  through  the  screw-driver  to  the  metal  of  the  engine 
cylinder,  instead  of  going  down  through  the  spark  plug  and 
across  its  air  gap.  While  the  screw-driver  is  in  this  position 
there  is  no  spark  at  the  spark  plug.  If  the  engine  changes 
its  speed,  when  each  spark  plug  is  tested,  the  ignition  is 
satisfactory.  On  the  other  hand,  if  the  speed  of  the  engine 
does  not  change  when  the  screw-driver  is  put  on  one  of 
the  spark  plugs,,  there  is  a  good  indication  that  the  ignition 
is  defective.  It  is  very  difficult,  however,  to  test  six-,  eight-, 
or  twelve-cylinder  engines  by  this  method,  as  it  is  difficult 
to  hear  a  momentary  change  of  speed  in  an  engine  with  a 
large  number  of  cylinders. 

The  same  voltage  that  will  make  an  ignition  spark  jump 
one  thirty-second  of  an  inch  across  the  air  gap  of  a  spark 
plug  inside  an  automobile  engine  cylinder  will  make  the 
spark  jump  at  least  a  quarter  of  an  inch  outside  the  cylinder. 
The  difference  is  due  to  the  greater  resistance  of  the  air 
gap  of  the  spark  plug  to  the  passage  of  the  spark  when  it 
must  go  through  a  compressed  explosive  mixture.  If,  there- 
fore, the  spark  jumps  across  one-quarter  of  an  inch  outside 
the  engine  cylinders,  it  is  likely  the  ignition  current  is  giving 
a  good  spark  inside  the  cylinder  unless,  of  course,  the  cur- 


MAGNETOS  163 

rent  is  going  through  a  crack  in  the  porcelain  of  the  spark 
plug. 

One  of  the  best  tests  of  a  spark  plug  is  to  take  off  the 
wire  carrying  the  ignition  current  and  hold  it  a  quarter 
inch  away  from  the  top  of  the  spark  plug.  If  there  is  a 
spark  jumping  across  this  air  gap  at  the  top  of  the  plug 
it  is  not  likely  the  trouble  is  with  the  spark  plug.  In  making 
this  test  care  should  be  taken  that  the  current  is  not  stopped 
from  going  through  the  spark  plug,  as  stopping  the  high 
voltage  current  may  burn  out  the  fine  wire  winding  of  the 
induction  coil.  Moreover,  if  the  tester  gets  his  fingers  on 
bare  connections  or  on  uninsulated  wires  when  making  this 
test,  he  is  likely  to  have  an  unpleasant  "shock." 

If  the  engine  misses  explosions  on  a  hill,  and  runs  satis- 
factorily on  the  level,  there  is  probably  some  trouble  with 
the  ignition  in  the  spark  plug.  Sometimes  it  is  difficult  to 
find  the  troublesome  cylinder  especially  if  it  stops  missing 
explosions  at  the  top  of  the  hill.  If  the  missing  occurs  with 
regularity  it  is  likely  the  air  gap  of  one  of  the  spark  plugs 
is  larger  than  it  should  be.  If  one  of  the  air  gaps  is  too 
wide,  the  points  should  be  pressed  together  to  the  proper 
distance. 

Correct  Length  of  Spark  Plugs.  It  is  not  advisable  to 
buy  all  kinds  of  spark  plugs  recommended  by  stores.  Some 
spark  plugs  picked  up  at  random  will  project  too  far  into 
the  cylinders  of  some  engines  so  that  the  wires  or  "points" 
at  the  air  gap  of  the  spark  plug  get  red  hot  and  may  ignite 
the  explosive  mixture  too  soon.  There  is  often  the  same 
difficulty  with  spark  plugs  which  have  very  thin  wires  or 
"points"  at  the  air  gap.  On  the  other  hand,  if  a  spark 
plug  is  too  short  the  air  gap  wires  cannot  enter  the  com- 
bustion space  and  are  in  "dead  gas."  It  is  best  to  use  the 
kind  of  spark  plug  that  goes  with  the  engine.  Cheap  spark 
plugs  are  dear  at  any  price,  as  the  high-voltage  current  is 
likely  to  go  through  the  porcelain. 

Care   of   Distributor.      If   an   engine    is    misfiring,    after 
finding  out  that  there  is  no  trouble  with  the  spark  plugs, 


164  GASOLINE  AUTOMOBILES 

the  distributor  should  be  examined.  The  cover  can  be  taken 
off  and  held  up  so  that  it  can  be  wiped  off  inside.  Some- 
times there  is  a  thin  coating  of  dirt  or  of  oxide  on  the 
contact  or  other  parts  and  the  ignition  current  does  not 
go  through  them  at  all  or  does  not  go  to  the  right  points. 
Because  of  such  a  coating  on  the  distributor  points,  the 
current,  in  taking  the  easier  path,  may  jump  five  or  six 
times  as  far,  rather  than  go  to  the  right  points.  Under  these 
unfavorable  conditions  the  cylinder  which  is  skipping  ex- 
plosions will  be  the  one  which  is  on  its  compression  stroke  at 
the  moment  so  that  its  spark  plug  is  in  highly  compressed 
explosive  mixture,  and  the  spark  goes  over  the  coating  of 
dirt  to  the  distributor  point  of  the  spark  plug  of  a  cylinder 
which  is  not  on  the  compression  stroke.  For  cleaning  the 
distributor,  it  is  not  necessary  to  remove  the  wires. 

Nearly  all  automobiles  except  the  Ford  make  have  a 
distributor,  and  in  this  automobile  the  timer  must  be  in- 
spected and  cleaned  in  very  much  the  same  way  for  the 
same  reasons. 

Preignition.  When  any  small  piece  of  metal  or  a  bit 
of  carbon  deposit  in  an  engine  cylinder  becomes  red  hot, 
it  will  ignite  the  explosive  mixture  at  the  moment  of  contact 
without  an  ignition  spark.  Such  "automatic"  ignition 
generally  takes  place  long  before  the  spark  is  made  by  the 
ignition  device,  and  thus  causes  a  considerable  loss  of  power. 
This  early  ignition  of  the  mixture  is  called  preignition. 
Recent  investigations  show  that  overheated  valves  and  bits 
of  carbon  scarcely  ever  cause  preignition  but  that  it  is  fre- 
quently caused  by'  overheated  "points"  at  the  air  gap  of 
spark  plugs.  Preignition  is  simply  tested  by  cutting  off  the 
ignition  current  at  the  switch  and  observing  whether  the 
engine  continues  to  ignite  the  charge  for  a  moment  in  one 
or  more  cylinders.  If  the  engine  has  a  cut-out  on  the  muffler, 
its  use  will  assist  in  this  test. 

Knocking  and  Related  Trouble.  It  will  be  noticed  some- 
times that  an  engine  makes  unpleasant  noises  called  knock- 
ing when  heavily  loaded.  When  going  up  a  steep  hill,  for 


MAGNETOS  165 

example,  the  throttle  valve  of  the  carbureter  is  opened  wider 
than  in  ordinary  operation  so  that  the  engine  takes  an  un- 
usually large  amount  of  explosive  mixture.  As  a  result 
there  is  higher  compression  in  all  the  cylinders,  which  causes 
exceedingly  rapid  combustion.  In  other  words,  because  of 
the  higher  compression,  there  is  quicker  combustion  of  the 
explosive  mixture  in  the  cylinders.  This  unpleasant  noise 
can  be  avoided  if  the  spark  lever  is  set  back  a  little  (retarded 
spark)  so  that  the  ignition  will  be  started  a  little  later  in  the 
cylinders. 

Number  of  Spark  Plugs.  Two  spark  plugs  in  each  engine 
cylinder  insure  more  rapid  ignition  and  increase  the  power 
of  the  engine  for  the  same  amount  of  gasoline  used.  Obvi- 
ously, the  advantage  of  two  spark  plugs  is  greatest  in 
cylinders  of  large  diameter.  In  a  test  of  an  engine  with 
cylinders  which  were  five  and  one-half  inches  in  diameter, 
four  per  cent  more  power  was  developed  with  two  spark 
plugs  than  with  a  single  spark  plug.  Engines  of  smaller 
diameter  would  similarly  give  more  power  with  two  spark 
plugs  but  the  percentage  increase  would  be  less.  Using  four 
spark  plugs  instead  of  one  in  a  single  large  engine  cylinder 
will  increase  the  power  more  than  ten  per  cent  without  increas- 
ing the  amount  of  gasoline  used. 

Reasons  for  Spark  Advance.  It  takes  some  time  for  the 
combustible  mixture  to  be  completely  ignited,  and  obviously 
ignition  should  be  complete,  when  the  piston  in  an  automobile 
engine  cylinder  begins  its  explosion  or  power  stroke.*  When 
starting  an  engine,  even  with  a  self-starter,  the  piston  moves  so 
slowly  that  if  the  explosive  mixture  is  ignited  before  the 
piston  gets  to  the  top  of  its  stroke  the  engine  may  start 
backward.  If  an  engine  is  being  started  by  hand  cranking, 
it  is  not  unusual  for  the  quick,  reverse  movement  of  the 


*  The  result  is  that  during  all  the  time  required  for  ignition,  the 
pressure  is  building  up  rapidly  in  the  cylinder  and  is  causing  a  back- 
ward pressure  on  the  piston  which  is  not  useful  as  "compression" 
pressure. — Journal  of  Society  of  Automotive  Engineers,  November,  1920, 
page  475. 


166  GASOLINE  AUTOMOBILES 

starting  crank  to  break  an  arm  or  a  collar  bone  of  the  person 
using  it.  It  takes  a  fraction  of  a  second  after  the  mixture 
is  ignited  before  there  is  an  explosion.  The  ignition  spark 
must,  therefore,  be  set  to  occur  at  a  different  piston  position 
for  starting  than  for  regular  operation.  When  an  engine 
is  at  normal  speed  and  the  piston  is  moving  rapidly  it  is 
necessary  to  start  the  combustion  of  the  explosive  mixture 
earlier  than  when  the  engine  is  being  started.  This  early 
ignition  is  called  the  spark  advance. 

After  the  engine  has  been  started  and  is  gaining  speed 
the  spark  control  lever  on  the  steering  wheel  should  be 
gradually  advanced  till  it  is  in  the  position  for  usual  running 
conditions.  It  should  not  be  advanced  so  far  that  the  pistons 
make  a  thumping  or  "pounding"  noise  in  the  cylinders. 
The  amount  of  the  advance  of  ignition  depends  on  the  three 
following  conditions  in  the  engine  cylinders: 

(1)  If  the  combustible  mixture  is  ignited  on  all  sides 

and  in  the  center  simultaneously  it  will  cause 
the  charge  to  burn  more  rapidly  just  as  when, 
in  burning  a  pile  of  brush,  it  burns  faster  if  the 
torch  is  applied  on  all  sides  instead  of  at  one 
point  only.  One  way  to  accomplish  this  is  to  use 
more  than  one  spark-plug  per  cylinder. 

(2)  If  the  combustible  mixture  were  agitated  within  the 

cylinder  or  rotated  fast  enough  so  that  most  of 
it  passed  the  spark  while  the  crank  moved  only 
a  little,  the  effect  would  be  the  same  as  if  the 
spark-plug  ran  around  the  edge  of  the  cylinder 
igniting  the  gas  on  all  sides  almost  simultane- 
ously. 

(3)  If   higher   compression   pressures   were   used,   the 

flame  would  travel  through  the  charge  much 
faster  and  would  at  the  same  time,  make  possible 
the  use  of  smaller  combustion-chambers.  This 
means  that  the  flame  would  not  be  required  to 
travel  so  far.  The  objection  to  using  high  com- 
pression is  that  it  causes  knocking. 


CHAPTER   VII 
ELECTRIC    STARTERS 

Starters  in  General.  Although  a  modern  gasoline  engine 
for  automobile  or  aeroplane  services  is  a  marvel  of 
mechanical  ingenuity  furnishing  power  with  less  weight 
than  any  other  kind  of  engine,  it  cannot,  with  all  its  wonder- 
ful improvements,  start  on  its  own  power  like  other  kinds 
of  engines  and  motors.  This  is  because  there  is  only  one 
power  stroke  to  three  idle  strokes.  Once  it  is  started,  how- 
ever, the  power  for  these  three  "waste"  strokes  is  supplied 
by  a  rapidly  rotating  flywheel.  For  starting,  external  power 
is  needed,  which  may  be  human  power  as  applied  in  "wind- 
ing" the  engine  crank  or  "stored"  power  as  used  in  a  start- 
ing motor. 

As  automobiles  are  now  equipped,  nearly  all  the  starting 
motors  (called  "self-starters")  are  of  the  electrical  kind. 
Few  mechanical  starters  are  now  used. 

Electric  Starters.  The  three  essential  parts  of  an  electric 
starter  are  (1)  an  electric  motor,  attached  either  directly  to 
the  flywheel  or  by  intermediate  gears  to  the  crank  shaft  of 
the  engine,  to  give  the  "cranking  power";  (2)  an  electric 
storage  battery  of  sufficient  current  capacity  to  drive  the  elec- 
tric motor  for  starting;  (3)  an  electric  generator  connected 
by  gearing  or  otherwise  to  the  crank  shaft  of  the  engine 
to  generate  the  electric  current  for  charging  the  storage  bat- 
tery. For  simplicity  of  statement,  it  will  be  assumed  that 
the  current  for  electric  lights  and  for  cylinder  ignition 
is  also  always  taken  from  the  storage  battery.  In  some  elec- 
tric starting  systems,  the  electric  motor  and  the  generator  are 
combined  as  will  be  explained  later.  This  combination  is 
called  a  starter-generator. 

167 


168  GASOLINE  AUTOMOBILES 

The  electric  storage  battery  and  the  electric   generator 
are  not  very  different  in  construction  from  the  usual  com- 
mercial types.     The  principles  underlying  the  operation  of 
storage  batteries  have  been  explained  (see  page  107),  and  the 
general  principles  of  electrical  design  of  electric  generators 
have  been  explained  in  the  Chapter  011  Magnetos   (see  page 
148).    A  generator  differs  in  essential  parts  from  a  magneto 
only  in  having  electro-magnets  instead  of  permanent  magnets. 
Permanent  magnets  are  made  of  specially  hardened  steel  and 
on  being  magnetized  retain  their  magnetism  without  much 
diminution  for  many  year's.     A  generator  resembling  a  mag- 
neto   would    not    be    satisfactory    for    charging    a    storage 
battery  as  the  amount  of  current  it  could  give  would  be  too 
small  for  practical  use.     Electro-magnets  which  are  much 
stronger  than  permanent  magnets  can  be  made  by  passing  a 
current  of  electricity  through  a  coil  of  wire  surrounding  the 
magnet.    By  the  use  of  electro-magnets,  electric  generators  of 
any  desired  capacity  can  be  made.    A  coil  of  wire  on  an  iron 
spool,  if  rotated  by  connection  to  the  shaft  of  an  automobile 
engine  in  a  magnetic  field,  will  have  electric  current  gen- 
erated in  it  just  as  in  a  magneto.     The  current  developed  in 
a  magneto  or  any  electric  generator  is,  however,  an  alternating 
current,  which  cannot  be  used  for  charging  a  storage  battery. 
In  order  to  use  electric  current  for  storage  battery  service  it 
must  come  from  an  electric  machine  as  direct  current.     The 
device  or  attachment  of  a  generator  for  changing  the  alter- 
nating to  direct  current  is  called  a  commutator.     It  consists 
of  short  copper  bars  which  are  insulated  from  each  other,  and 
each  two  bars  diametrically  opposite,  are  connected  by  a  wire 
loop  wound  over  the  armature.    As  actually  constructed,  the 
commutator  and  armature  coils  are  attached  to  the  shaft  and 
firmly  bound  together.     Carbon  brushes  bear  on  the  curved 
surface  of  the  commutator  to  "gather"  the  electric  current 
in  the  armature  and  carry  it  to  the  terminals  of  the  storage 
battery,  the  lights,  the  induction  coils,  etc.     Connected  to  the 
main  wires,  carrying  the  electric  current  from  the  armature, 
are  small  branch  wires  which  take  some  of  the  current  to  the 


ELECTRIC  STARTERS  169 

electro-magnets  in  the  frame,  called  the  field  magnets. 
Bearings  for  the  shaft  are  on  the  end  covers.  One  cover 
is  usually  made  flat  and  the  other  with  an  extension, 
which  when  in  place  is  the  cover  for  the  commutator.  As 
thus  assembled,  the  brushes  for  carrying  away  the  current 
generated  are  inside  the  commutator  cover.  There  is  usually 
provision  for  inspection  of  the  operation  of  the  brushes  on  the 
commutator. 

The  starting  motor  should  be  of  sufficient  power  to  turn 
the  engine  crank  shaft  between  one  hundred  and  two  hundred 
revolutions  per  minute  to  get  dependable  ignition  conditions; 
but  the  power  is  needed  for  only  a  few  seconds.  Because  of 
this  short  duration  of  service,  a  starting  motor  can  be  made 
much  smaller  than  an  ordinary  type  of  electric  motor,  in- 
tended for  continuous  service,  without  excessive  heating  in  its 
coils  and  bearings.  Large  wires  are  needed  to  carry  the  large 
current,  sometimes  as  much  as  two  hundred  amperes  in  the 
motors  for  large  engines.  The  size  of  storage  battery  used 
with  electric  starting  systems  is  not  large  enough  to  withstand 
the  drain  of  so  much  current*  for  any  considerable  time. 

Starting1  Motor  Drives.  After  an  automobile  engine  has 
been  started  it  gains  speed  rapidly  and  gets  very  quickly  to 
a  speed  of  about  one  thousand  revolutions  per  minute.  Now, 
if  no  means  were  provided  for  disconnecting  the  electric 
starting  motor  from  the  engine  after  the  engine  begins  run- 
ning itself,  with  increasing  speed,  the  motor  would  certainly 
be  damaged  by  the  excessive  generation  of  current  in  its  coils ; 
for  the  reason  that  when  an  electric  motor  receives  electric 
current  at  a  certain  voltage,  it  can  be  used  to  drive  a  machine 
or  engine,  but  if  the  machine  or  engine  receives  power  so 
that  it  goes  faster  than  the  normal  speed  of  the  motor,  it 
will  no  longer  take  current  but  will  act  like  an  electric 
generator  and  make  its  own  current.  Also  the  low-speed 


*The  power  of  a  motor  (kilowatts)  is  the  product  of  amperes  times 
volts  divided  by  one  thousand.  In  the  case  mentioned,  it  is  assumed 
there  are  three  storage  cells  giving  six  volts.  Therefore,  kilowatts  of 
motor  =  200  X  6  -r-  1000  =  1.2. 


170 


GASOLINE  AUTOMOBILES 


bearings  of  the  electric  starting  motor  could  not  withstand 
the  high  speed  it  would  have  as  a  generator.  For  these 
reasons  the  starting  motor  must  not  remain  in  geared  or  in 
similar  connection  with  the  engine  crank  shaft  after  the  engine 
begins  running  on  its  own  power.  This  disconnection  when 
the  engine  is  running  should  not  be  left  to  the  chance  thought- 
fulness  of  the  driver.  The  usual  method  is  to  use  an  automatic 
clutch. 

One  method  of  driving  the  engine  when  starting  is  by 
means  of  a  gear  wheel  on  the  electric  starting  motor  which 


Fie.  147.— Typical  Delco  Electric  Starting  Motor  (and  Generator). 

can  be  made  to  slide  in  and  out  of  mesh  with  gear  teeth  on 
the  rim  of  the  engine  flywheel.  This  is  the  method  used,  for 
example,  on  the  Buick  automobile  (Fig.  147).  A  chain  drive 
is  used  on  the  Ford  automobile  (Fig.  148). 

The  device  most  commonly  used  to  prevent  driving  the 
electric  motor  at  too  high  speed  when  the  engine  starts  under 
its  own  power,  depends  for  its  action  on  a  weighted  gear 
wheel  which  is  automatically  thrown  out  of  mesh  with  the 
gear  teeth  on  the  flywheel  when  the  engine  gets  sufficient 
speed.  This  automatic  device  is  called  the  Bendix  drive,  and 
is  shown  in  Figs.  149,  150,  and  151.  When  the  starting  pedal 


ELECTRIC  STARTERS 


171 


or  switch  closes  the  electric  circuit  of  the  starting  motor,  the 
armature  starts  to  rotate  its  shaft,  which  has  screw  threads  B 
at  one  end.  Fig.  149  shows  the  normal  position  of  the  gear 
wheel  A,  which  has  internal  threads  to  fit  corresponding 


Motor  Generator 


FIG.  148. — Examples  of  Chain  Drives  for  Electric  Starters. 

threads  on  the  shaft  at  B,  and  in  this  model  is  weighted  on 
one  side  (eccentrically)  at  W.  Because  of  this  eccentric 
weight,  and  due  to  its  inertia,  the  gear  wheel  A  will  not  rotate 
immediately  with  the  shaft,  but  will  run  forward  on  the 


FIG.  149. — Bendix 
Drive  Disconnected. 


FIG.-  150— Shifting 
Position. 


FIG.  151.— Gears 
Connected. 


revolving  screw  threads  B,  as  shown  in  Fig.  150,  until  it 
meshes  with  the  teeth  on  the  flywheel  as  in  Fig.  151.  The 
shaft  carrying  the  threads  B  is  hollow  and  is  connected  to  the 
armature  shaft  by  means  of  spring  S.  If  the  teeth  of  the  gear 
wheel  and  those  on  the  flywheel  do  not  mesh  when  they  first 


172  GASOLINE  AUTOMOBILES 

come  together,  the  spring  S  will  allow  the  gear  wheel  to 
revolve  until  the  teeth  do  mesh.  When  the  gear  wheel  is 
meshed  with  the  flywheel  as  in  Fig.  151  the  spring  S  will  be 
tightly  compressed  and  the  power  of  the  electric  motor 
becomes  effective  for  turning  the  engine. 

The  spring  S  acts  like  a  cushion  when  turning  the  engine 
over  against  compression,  or  if  the  engine  backfires.  As  soon 
as  the  speed  of  the  engine  is  higher  than  that  of  the  starting 
motor  the  flywheel  will  drive  the  gear  wheel  A  at  a  higher 
speed  than  that  of  the  armature  shaft  of  the  starting  motor, 
so  that  the  gear  wheel  will  be  turned  in  the  opposite  direction 
on  its  screw  thread  and  be  automatically  released  from  the 
teeth  on  the  flywheel.  The  starting  switch  must  be  released 
as  soon  as  the  engine  starts  on  its  own  power.  If  this  is  not 
done  the  starting  motor  shaft  will  increase  in  speed  also  and 
the  gear  A  will  not  disengage.  This  device  thus  prevents  the 
engine  from  driving  the  starting  motor. 

"When  the  starting  motor  drives  the  engine  by  means  of  a 
silent  chain  or  similar  method  (see  Fig.  148)  as  used  on 
Ford,  Dodge,  and  Franklin  automobiles,  for  example,  the 
engine  is  prevented  from  driving  the  motor  by  the  use  of  an 
over-running  clutch,  which  slips  when  the  engine  tends  to 
drive  the  motor. 

A  typical  construction  of  an  over-running  clutch,  shown 
in  Fig.  152,  consists  of  a  star-shaped  inner  member,  which  is 


FIG.  152. — Overrunning  Clutch. 

keyed  to  the  shaft,  free  to  rotate  inside  the  intermediate  gear. 
Four  rollers  R  are  inserted  between  these  two  members  in  such 
a  way  that  they  will  bind  in  the  angles  of  the  star  when  the 
shaft  is  turned  in  one  direction,  but  will  rest  free  from  tho 
outer  member  if  the  shaft  is  turned  in  the  opposite  direction. 


ELECTRIC  STARTERS  173 

There  is  also  another  type  of  starting .  motor  drive  which 
depends  for  its  action  on  the  magnetic  pull  of  the  strong 
electromagnets  attached  to  the  motor  to  draw  the  entire 
armature  and  the  gear  wheel  at  the  end  of  its  shaft  into  a 
position  where  the  gear  wheel  meshes  with  teeth  on  the  fly- 
wheel. In  this  device  the  armature  is  mounted  on  a  hollow 
shaft  which  has  a  slot  in  the  middle  into  which  is  fitted  a 
projection  on  the  inside  of  the  hub  of  a  small  gear  wheel.  A 
shifting  rod  inside  the  hollow  shaft  and  fastened  to  the 
projection  on  the  hub  of  the  gear  wheel,  is  attached  at  one 
end  to  a  large  piece  of  soft  iron  which  fits  inside  a  coil  of 
wire.  When  the  current  from  the  storage  battery  goes 
through  the  coil  the  piece  of  soft  iron  is  pulled  into  the  coil 
and  draws  with  it  the  shifting  rod  and  the  attached  gear 
wheel,  so  that  it  is  brought  into  mesh  with  the  teeth  on  the 
flywheel.  All  starting  motors  require  a  large  current  at  the 
moment  they  start  to  revolve;  and  since  this  large  current 
flows  also  through  the  coil  of  the  shifting  magnet,  it  gives 
sufficient  magnetic  pull  to  overcome  the  tension  of  a  spiral 
spring  on  the  shaft  intended  to  oppose  this  motion.  As  soon 
as  the  teeth  011  the  gear  wheel  mesh  with  the  teeth  on  the 
flywheel  the  current  required  to  turn  the  engine  is  large 
enough  in  the  electromagnet  to  hold  the  gear  wheel  in  mesh 
against  the  tension  of  the  spring.  But  as  soon  as  the  engine 
runs  on  its  own  power,  the  current  needed  for  the  starting 
motor  is  very  small  and  the  coil  of  the  electromagnet  is 
weakened,  so  that  the  spring  is  stronger  than  the  magnetic 
pull  and  the  gear  wheel  is  drawn  out  of  contact  with  the  fly- 
wheel. 

Starting  Motor  Switch.  The  Delco  starting  motor  switch 
is  shown  by  Fig.  153.  It  is  installed  on  the  floor  boards  of 
the  automobile  and  is  operated  by  the  driver's  foot.  By 
pressing  the  foot  button  a  connection  is  made  between  the 
battery  lead  and  the  starting  motor  lead.  The  leads  are  heavy 
copper  cables,  usually  No.  0  or  No.  00  size,  made  of  stranded 
wire,  heavily  insulated.  The  leads  are  also  very  often  protected 
against  chafing  by  an  outside  winding  of  metal,  called  armor. 


174  GASOLINE  AUTOMOBILES 

The  terminals  of  the  switch  are  large  and  imbedded  in 
insulation.  The  size  is  important  because  of  the  large  amount 
of  current  used  by  the  starting  motor  and  the  insulation  is 
very  necessary  because  the  battery  would  be  short-circuited 
if  the  battery  lead  became  grounded.  The  switch  terminals 
are  also  self-cleaning,  which  is  desirable  because  heavy  sparks 


SetfCkam'ng 

Double  Cup  Contact 


Battery  Lead 
FIG.  153. — Delco  Starting  Motor  Switch. 

occur  when  a  circuit,  in  which  a  large  current  is  flowing,  is 
suddenly  broken. 

Reverse  Current  Cut-out.  In  some  starting  and  lighting 
systems  an  automatic  switch  operated  by  electromagnets  is 
connected  in  the  battery  charging  circuit  between  the  electric 
generator  and  the  storage  battery  for  the  double  purpose: 
(1)  to  make  electrical  connection  between  the  generator  and 
the  battery  when  the  generator  voltage  is  high  enough  to 
charge  the  battery;  (2)  to  cut  off  this  charging  current  from 
the  battery  as  soon  as  the  voltage  of  the  generator  falls  below 
the  battery  voltage  (usually  because  of  low  speed).  This 
device  is  necessary  when  the  engine  is  not  running,  as  without 
some  arrangement  of  this  kind  the  battery  would  discharge 
itself  by  sending  its  current  through  the  wires  of  the  gen- 
erator. One  type  of  an  apparatus  for  this  purpose  is  shown 
diagrammatically  in  the  center  of  Fig.  154.  It  consists  of  a 
vertical  iron  magnet;  a  winding  of  fine  wire,  called  the 
voltage  coil;  a  winding  of  coarse  wire,  called  the  current  coil; 
and  a  set  of  contact  pieces  which  are  normally  held  apart  by 
the  small  spiral  spring  as  shown.  One  of  these  contact  pieces 


ELECTRIC  STARTERS 


175 


is  over  the  top  of  the  iron  magnet.  This  magnet,  by  its  pull, 
draws  the  contact  pieces  together  when  the  voltage  of  the 
generator  becomes  six  and  a  half  or  seven  volts  (if  the  storage 
battery  has  three  cells)  or  between  thirteen  and  fourteen 
volts  (if  six  cells  in  the  battery).  These  voltages  usually 
correspond  to  an  automobile  speed  on  direct  drive  (without 
gearing)  of  about  ten  miles  per  hour. 


Fuse 


Series  Fie  id  Winding 
Ma  in  Brushes - 


..Shunt  Field  Wmding 
•••Jhirc/  Brush 


JoHorn 


To  Lighting  and  Ignition 
Switch 


FIG.   154. — Diagram  Showing  Reverse  Current  Cut-out. 


When  the  direction  of  the  current  is  such  as  to  charge  the 
storage  battery,  the  voltage  coil  and  the  current  coil  exert 
their  magnetic  pull  in  the  same  direction ;  that  is,  to  keep  the 
points  of  the  contact  pieces  together,  so  that  the  current  from 
the  generator  goes  through  the  battery  to  charge  it.  When, 
however,  the  voltage  of  the  generator  falls  below  that  of  the 
battery  and  the  battery  begins  to  discharge  through  the 
wiring  of  the  generator,  the  directions  of  the  magnetic  pull 


176  GASOLINE  AUTOMOBILES 

of  the  voltage  coil*  and  the  current  coil  are  opposite,  so  that 
the  contact  pieces  are  released  and  the  flow  of  current  from 
the  battery  is  stopped. 

The  operation  of  the  cut-out  can  be  tested  by  observing  the 
light  produced  by  the  headlights  when  the  speed  of  the  engine 
is  varied.  The  test  can  best  be  made  when  the  automobile  is 
not  running.  If  the  engine  speed  is  gradually  increased  to 
that  corresponding  to  about  ten  miles  per  hour  of  the  auto- 
mobile, the  lights  will  become  suddenly  brighter.  At  the 
moment  of  this  change  in  brilliancy  the  current  comes  from 
the  generator  instead  of  from  the  battery;  and  the  generator 
voltage  for  charging  is  about  one  and  a  half  volts  higher  than 
the  battery  voltage  (when  the  battery  has  three  cells). 

Starting  systems,  like  the  Delco  (Fig.  147),  which  do  not 
have  a  current  cut-out  device  of  this  kind,  avoid  most  of  the 
difficulty  by  designing  the  generator  to  give .  the  required 
voltage  for  charging  the  storage  battery  when  the  speed  of  the 
automobile  is  only  about  seven  miles  per  hour.  At  very  low 
engine  speeds  when  the  voltage  of  the  generator  is  not  high 
enough  to  charge  the  battery  there  will  be  a  small  amount  of 
current  discharged  from  the  battery  through  the  generator 
wires.  In  systems  of  this  kind  the  ignition  switch  cuts  off 
the  battery  current  from  the  generator.  This  switch,  there- 
fore, should  never  be  left  closed  when  the  engine  is  not  run- 
ning, because  in  several  hours  this  loss  of  current  would 
practically  discharge  the  battery. 

Third  Brush  Regulation.  In  all  well  designed  electric 
starting  systems  there  is  a  means  by  which  damage  to  the 
storage  battery  by  overcharging  may  be  prevented.  A  suit- 
able device  for  this  purpose  should  give  increasing  current 
for  charging  as  the  speed  is  increased  up  to  about  twenty 
miles  per  hour,  but  at  higher  speed  the  electric  current  should 
be  constant  or  should  be  reduced. 


*The  current  of  the  voltage  coil  is  shunted  to  a  grounded  connection, 
and  is  not  affected  by  the  change  of  direction  of  the  charging  or  battery 
current. 


ELECTRIC  STARTERS  177 

When  the  speed  is  about  forty  to  fifty  miles  per  hour,  the 
generator  current,  as  a  rule,  will  be  only  about  a  third  of  the 
maximum  value.  There  is  a  distinct  advantage  in  this  method 
of  regulation  in  that  the  -maximum  current  or  charging  rate 
for  the  battery  is  obtained  at  the  normal  driving  speeds. 

The  method  most  used  is  called  third  brush  regulation 
and  is  difficult  to  explain  without  a  full  discussion  of  the 
theory  of  electric  generators.*  Briefly  stated,  however,  this 
method  is  usually  applied  to  electric  generators  with  only  two 
electromagnets,  which  normally  would  have  only  two  brushes 
for  collecting  the  current  on  opposite  sides  of  the  commutator, 
but  in  this  method  a  third  brush  is  put  on  the  commutator 
between  the  other  two.  It  is  a  well-known  fact  that  as  the 
speed  and  amount  of  current  of  such  a  generator  increase 
the  magnetic  field  due  to  the  electromagnets  (field  magnets) 
becomes  distorted  and  unequally  distributed.  By  taking  the 
current,  used  for  the  magnetization  of  the  field  magnets,  from 
two  brushes .  that  are  not  diametrically  opposite  a  variable 
current  is  obtained,  which  tends  to  get  weaker  as  the  speed 
of  the  generator  is  increased.  The  position  also  of  the  third 
brush  may  be  changed  so  as  to  alter  the  maximum  charging 
current. 

Adjustment  of  Third  Brush  Device.  The  amount  of  cur- 
rent permissible  for  charging  depends  on  the  construction  and 
size  of  the  battery  plates.  In  the  Delco  and  Westinghouse 
systems,  for  example,  the  maximum  charging  rate  is  about 
fifteen  amperes,  and  on  the  North  East  system  it  is  only  about 
six  amperes.  If  the  ammeter  on  the  instrument  board  indi- 
cates a  higher  current  than  the  maximum  charging  rate, 
adjustment  can  be  made,  if  the  third  brush  method  is  used, 
by  shifting  the  third  brush  slightly  in  the  opposite  direction 
to  the  rotation  of  the  armature.  Shifting  the  third  brush  in 
the  direction  of  rotation  of  the  armature  increases  the  charg- 
ing current.  Whenever  the  third  brush  is  moved  in  either 


*For  detailed  explanation  see  Consoliver  and  Mitchell's  Automotive 
Ignition  Systems,  published  by  McGraw-Hill  Book  Co.,  New  York. 


178  GASOLINE  AUTOMOBILES 

direction,  care  should  be  taken  that  it  makes  good  contact 
with  the  commutator.  If  the  contact  is  not  good,  the  brush 
will  seat  imperfectly  and  the  charging  current  will  increase 
only  when  the  brush  seats  properly  after  wearing  into  place. 

Eecent  practice  in  automobile  engineering  tends  to  the 
simplification  of  starting  and  lighting  systems  and  for  this 
reason  the  third  brush  method  of  regulating  charging  current 
is  superseding  most  other,  more  complicated  methods. 

In  case  the  battery  is  disconnected,  as  for  example,  when 
taken  out  for  recharging,  and  the  automobile  is  operated  with 
another  source  of  current,  precaution  must  be  taken  that  the 
generator  does  not  "build  up"  voltage  which  would  damage 
the  winding  of  the  armature.  One  way  to  accomplish  this  is 
to  "ground"  the  main  generator  terminal  by  attaching  it 
firmly  to  a  clean  surface  on  the  automobile  frame.  Another 
way  is  to  remove  the  shunt  field  fuse  (Fig.  154). 

Since  one  terminal  of  a  storage-battery  is  always  grounded, 
a  dangerously  large  current  would  be  taken  from  the  battery 
if  by  accident  or  deterioration  of  materials  the  insulation 
should  be  removed  from  wires  which  are  near  enough  to  the 
engine  or  to  the  automobile  frame  to  touch  either  of  them. 
For  protection  from  this  danger  in  the  Delco  system  there  is 
a  vibrating  circuit  breaker  in  the  main  wiring  system  next  to 
the  ammeter.  This  circuit  breaker  prevents  excessive  current 
in  the  same  way  as  when  fuses  are  used ;  but  with  the  advan- 
tage that  after  the  cause  of  the  excessive  current  has  been 
removed,  the  apparatus  goes  automatically  into  normal 
operation  again.  It  is  not  needed  for  the  wiring  of  the 
ignition  system  as  the  safety  resistance  coil  or  similar  device 
on  the  induction  coil  prevents  excessive  ignition  current,  but 
the  wires  for  the  lights  and  horn  have  no  protective  device 
except  this  main  circuit  breaker.  Whenever  an  excessive  cur- 
rent flows  through .  the  circuit  breaker,  it  opens  the  circuit 
intermittently,  causing  a  clicking  sound.  This  circuit  breaker 
can  be  operated  by  hand  by  pressing  on  a  small  flat  disk  on 
the  back  of  the  switchboard  between  the  ammeter  and  the 
ignition  switch. 


ELECTRIC  STARTERS 


179 


North  East  System.  In  the  North  East  system  shown  in 
Fig.  155  the  starting  motor  and  electric  generator  are  a  single 
unit,  with  only  one  armature,  one  commutator,  and  one  set  of 
windings  on  the  field  magnets.  In  this  system  the  third  brush 
is  set  on  the  commutator  in  such  a  position  that  it  can  be 
adjusted  by  turning  the  screw  in  the  end  cap  or  cover  over 
the  brushes.  The  starter-generator  is  mounted  at  the  left- 
hand  side  of  the  engine,  and  is  connected  to  the  engine  crank 


Igm 


Starting 'Snitch  ancf 
Reverse  Current 
Cuf-  out 

J 


Lighting  and  Ignition      Horn  Button 
Switch 

FIG.  155. — North  East  Starting  and  Lighting  System. 


shaft  by  a  chain  drive.  The  generator  is  driven  by  a  ratchet 
or  over-running  clutch. 

When  the  engine  speed  is  350  revolutions  per  minute  or 
over,  the  starter-generator  changes  automatically  into  a  gen- 
erator and  supplies  current  for  charging  the  battery  as  well  as 
for  the  lighting  and  ignition. 

A  typical  two-unit  system  which  has  a  starting  motor  and 
a  generator,  each  as  separate  units,  is  shown  diagrammatically 
in  Fig.  156.  This  system  as  applied  to  a  Ford  automobile  is 
shown  in  more  detail  in  Fig.  156A.  The  Westinghouse 
system  shown  in  Fig.  157  has  two  units,  and  many  of  the 
Delco  starting  and  lighting  systems  have  this  arrangement. 


180 


GASOLINE  AUTOMOBILES 


Westinghouse  Starting  and  Lighting  System.  Some  recent 
Westinghouse  designs  use  the  usual  third  brush  method  of 
regulating  the  amount  of  current  going  through  the  battery 


FIG.  156. — Diagram  of  Two-unit  Electric 
Starting  System. 

for  charging.  A  method  of  current  regulation  by  automatic 
voltage  control  is  applied  in  the  Westinghouse  design  shown 
in  Fig.  157.  The  device  used  is  near  the  center  of  the  figure  and 


Generator  ......  .  --  Blue-  Commut/rfar  W/ra  -to  No.  I  Terminal 

•Ground  -to  Housfnq-'     /  .-  ted  "  "    "M>.2        " 

l/f    ••  ;'  .-Hue         ••  »    "NbJ      - 

:   '     sGrttn 


ttn       "  "    "Mo.4      •• 

-Magneto  Contact 


.  .  Ammetar  or  Otarginglndicator 


Coil  Terminal 
...•Stltcfive  Snitch 
..-Horn 


'••Ho.  6  Grey  ••     •>       •>  Headlight 

Fie.  156-A.— Liberty  Starting  and  Lighting  System  for 
Ford  Automobile. 


is  marked  "regulator  and  cut-out."  This  kind  of  constant 
voltage  mechanism  is  much  more  expensive  to  construct  than 
the  third  brush  device,  and  is  therefore  not  so  much  used. 


ELECTRIC  STARTERS 


181 


When  the  electric  generator  is  driven  at  a  speed  which  is 
too  low  to  give  the  required  voltage  for  charging  the  battery 


the  regulator  contacts  shown  in  the  figure  are  closed;  but 
they  are  opened  when  the  speed  is  sufficient  to  produce  cur- 
rent at  the  charging  voltage  of  the  battery.  When,  however, 


182  GASOLINE  AUTOMOBILES 

the  voltage  and  current  tend  to  exceed  the  established  rate  the 
magnetic  pull  of  the  electromagnets  under  the  contact  arm  is 
increased  and  pulls  open  the  contact  points.  The  effect  of 
this  opening  of  the  contacts  is  to  put  additional  resistance 
into  the  circuit  supplying  current  to  the  electromagnets  (field 
magnets)  011  the  generator,  with  a  resulting  drop  in  voltage 
and  current  so  that  the  magnetic  pull  of  the  electromagnets 
under  the  contact  arm  is  immediately  decreased  so  that  the 
contacts  close  again.  This  opening  and  closing  of  the  contacts 
is  so  rapid  that  the  voltage  and  current  are  held  constant. 
The  maximum  charging  current  can  be  increased  by  turning 
the  regulating  adjusting  screw  on  top  of  the  contact  arm  so  as 
to  increase  the  tension  of  the  spring  on  the  contact  points. 
The  charging  current  in  the  apparatus  should  not  exceed 
twelve  amperes. 

The  Westinghouse  system  shown  in  Fig.  157  has  a  Bendix 
drive  on  the  starting  motor ;  but  this  system  is  sometimes  made 
with  an  electromagnetic  gear  shift  on  the  starting  motor  (see 
page  173). 

Large  electric  head  lights  require  a  great  deal  of  current. 
Unless  the  storage  battery  is  fully  charged  the  requirements 
of  lighted  head  lights  for  electric  current  will  reduce  the 
battery  capacity  so  that  there  will  be  little  reserve  power  for 
running  an  electric  starter,  especially  in  cold  weather  when  the 
starter  requires  a  large  amount  of  current.  It  is  a  good  idea, 
therefore,  to  turn  off  the  head  lights  if  there  is  likelihood  of 
difficulty  in  starting  the  engine. 

On  many  automobiles  there  is  a  device  for  "dimming" 
the  electric  head  lights  which  reduces  the  amount  of  light  by 
passing  the  electric  current  through  a  high-resistance  coil.  As 
this  device  is  used  there  are  two  electric  switches  controlling 
the  lights.  One  of  these  is  for  the  circuit  including  the 
"dimming"  resistance;  the  other  for  the  "undimmed"  lights. 
The  dim  lights  are  intended  for  use  when  the  automobile  is 
standing  or  when  passing  other  automobiles  if  the  bright 
lights  are  objectionable  because  of  glare.  The  best  way  to 
use  switches  of  this  kind  is  to  close  the  "dimming'*  switch 


ELECTRIC  STARTERS  183 

whenever  the  switch  on  the  circuit  for  bright  lights  is  closed. 
It  is  then  a  very  simple  matter  in  passing  other  automobiles 
to  open  quickly  the  switch  for  bright  lights  and  the  electric 
current  will  continue  to  go  through  the  lights  of  the  "  dim- 
ming" circuit.  The  other  way  of  using  these  switches  is 
very  ojectionable :  that  is,  by  opening  the  switch  for  bright 
lights  and  then  closing  the  switch  for  "dimming."  This 
method  leaves  a  short  interval  when  the  head  lights  give  no 
light  at  all.  There  is  a  further  advantage  of  having  the 
"dimming"  switch  closed  whenever  the  head  lights  are  used, 
as  it  is  not  very  likely  that  one  will  then  leave  an  automobile 
standing  without  lighted  head  lights.  There  is  a  small  elec- 
trical loss  in  the  use  of  a  high-resistance  "dimming"  device 
of  this  kind;  but  practically  all  this  loss  is  eliminated  when 
the  two  switches  are  used  together  as  explained,  because  then 
very  little  electric  current  goes  through  the  "dimming" 
resistance. 

It  is  a  good  idea  for  owners  of  automobiles  to  study  the 
wiring  diagrams  of  their  automobiles  and  to  trace  from  time 
to  time  the  current  from  the  battery  through  each  light, 
through  the  ignition  system,  through  the  horn,  and  through 
every  other  electrical  device  used  on  the  automobile,  including 
the  generator  and  starting  motor.  It  is  also  a  good  practice 
for  the  owner  to  carry  the  wiring  diagram  of  his  automobile 
when  touring  so  as  to  give  information  and  assistance  to 
inexperienced  garage  men. 


CHAPTER   VIII 
CLUTCHES,  TRANSMISSIONS,  AND  DIFFERENTIALS 

Any  kind  of  gasoline  engine  suitable  for  automobiles  has 
the  disadvantage  of  not  being  able  to  start  when  loaded  or 
to  draw  any  considerable  load  at  very  low  speed.  Inter- 
mediary devices  called  clutches  for  starting  and  speed-change 
gears  or  transmission  gears  for  speed  changes  are  therefore 
necessary  to  make  the  engine  adaptable  for  general  road 
service.  In  this  respect  a  gasoline  engine  is  unlike  a  steam 
engine  which  is  adaptable  for  such  service  without  these  inter- 
mediary devices.  When  a  steam  engine  is  started,  full  boiler 
pressure  can  be  immediately  effective  behind  the  engine  piston 
with  maximum  available  force.  The  same  condition  exists 
for  the  use  of  this  kind  of  engine  at  very  slow  speed.  In 
fact  a  steam  engine  of  good  design  will  usually  have  slightly 
more  tractive  pull  at  slow  speed  than  at  high.  The  steam 
engine  is  also  self-starting  without  auxiliary  devices. 

In  spite  of  these  disadvantages  in  starting  and  slow-speed 
power,  the  gasoline  engine  has  so  many  other  advantages 
especially  as  regards  simplicity  of  operation  and  fool-proof 
construction,  that  it  has  almost  "universal"  application  in 
automobile  service. 

Clutches.  A  gasoline  automobile  engine  must  be  set  in 
motion  before  it  can  take  up  its  load,  so  that  a  device  must 
be  provided  to  detach  it  from  the  rest  of  the  automobile 
mechanism  in  order  to  get  it  started,  and  such  a  starting 
device  must  be  arranged  so  that  after  the  engine  is  started, 
it  will  permit  gradually  applying  the  driving  load  of  the 
automobile  mechanism.  A  device  for  this  purpose  is  called 
a  clutch.  There  are  two  general  types:  (1)  the  cone  clutch, 
and  (2)  the  disk  clutch.  Both  types  depend  for  their  action 
184 


CLUTCHES,  TRANSMISSIONS,  AND  DIFFERENTIALS     185 

on  the  friction  of  relatively  large  surfaces.  Ideal  friction 
materials  for  this  service  must  permit  some  slipping  so  as  to 
permit  gradually  increasing  speed. 

The  friction  materials  most  used  are  asbestos  fabric  or 
leather  for  one  surface  and  cast  iron  for  the  other.  Dry 
leather  is  a  good  material  but  when  wet  or  greasy,  its  frictional 


FIG.  158. — Cone  Clutch  Engaged.       Fie.  159. — Cone  Clutch  Disengaged. 

value  is  cut  in  half.    Cork  on  cast  iron  is  also  sometimes  used. 
It  is  not  much  affected  by  water  or  oil  as  to  friction  value. 

Cone  Clutches.  A  typical  cone  clutch  is  shown  in  Figs. 
158  and  159  in  its  closed  and  open  positions.  It  consists  in 
essential  parts  of  a  fabric  covered  metal  cone  C  which  can 
be  held  tightly  by  springs  against  the  inside  of  the  iron  fly- 
wheel F  on  the  engine  shaft.  The  cone  C  is  mounted  on  a 


186 


GASOLINE  AUTOMOBILES 


sleeve  or  hub  M  which  is  arranged  to  slide  back  and  forth 
on  the  shaft  S  so  as  to  engage  or  disengage  the  cone  from 
the  flywheel.  At  the  rear  end  of  the  sleeve  M  is  a  ring  R 
connecting  the  clutch  with  the  clutch  foot  pedal  P  which  is 
located  in  the  automobile  in  front  of  the  steering  column. 
The  operation  of  releasing  the  clutch  from  the  flywheel  is 
as  follows :  Pressure  on  the  clutch  foot  pedal  P  is  transmitted 
by  a  connecting  lever  L  to  the  yoke  T  fitted  around  the  top 
of  the  ring  R.  By  this  movement  the  cone  C  is  pulled  away 
from  the  flywheel  F  against  the  tension  of  the  springs  T,  T. 


Clutch  Disc 
Drum 


FIG.  160. — Diagram  of  Disk  Clutch. 

When  pressure  on  the  clutch  foot  pedal  is  removed,  the  lever 
and  yoke  fall  back  into  their  original  position  and  the  springs 
T,  T,  by  their  tension  hold  the  cone  C  and  the  flywheel  in 
close  engagement  so  that  they  turn  together  and  transmit 
the  engine  power;  usually,  however,  through  intermediary 
gears  a^id  shafts,  to  the  rear  axle  of  the  'automobile. 

Multiple  Disk  Clutches.  A  section  through  a  disk  clutch 
or  what  is  commonly  called  a  multiple  disk  clutch,  is  shown 
in  Pig.  160.  In  essential  parts  it  consists  of  a  series  of 
alternate  driving  and  driven  disks.  The  driving  disks  A,  A, 
receive  the  power  from  the  flywheel  F  on  the  engine  shaft 
by  the  bolts  0,  0.  In  this  type  of  clutch  the  driving  disks 


CLUTCHES,  TRANSMISSIONS,  AND  DIFFERENTIALS     187 

are  thin  steel  plates,  fastened  together  by  bolts.  The  driven 
disks,  B,  B,  consist  of  plates  sometimes  with  holes  in  them 
into  which  pieces  of  cork  are  pressed.  In  the  position  for 
transmitting  power  the  tension  of  the  clutch  spring  T  holds 
the  driving  disks  A,  A,  and  driven  disks  B,  B,  in  close  contact. 
Pressure  on  the  clutch  foot  pedal  compresses  the  clutch  spring 
T  so  that  the  two  sets  of  disks  separate,  and  the  driving  disks 
gradually  come  to  rest  and  stop  the  automobile. 

The  driving  plates  of  disk  clutches,  also,  are  often  thin 
disks   faced   with   molded   asbestos   fabric,   which   has   been 

/^  /  ^x^^   -\      >      : 

RRK 


FIG.  161.— Multiple  Disk  Cluteh. 

treated  with  linseed  oil  and  baked,  and  the  driven  disks  are 
plain  steel  plates. 

A  modification  of  this  diagrammatic  arrangement  is  shown 
in  Fig.  161  in  which  the  driving  disks  are  connected  to  the 
drum  D  on  the  flywheel  by  sliding  projections  P,  P,  P,  fitting 
loosely  into  grooves  or  slots  G,  G,  G. 

The  holding  power  of  a  disk  type  of  clutch  is  the  sum 
of  the  holding  powers  of  the  several  disks.  Therefore,  by 
increasing  the  number  of  disks,  the  holding  power  of  the 
clutch  is  increased.  The  advantage  of  this  type  over  the  cone 
clutch  is  that  a  very  large  total  frictional  surface  can  be 
obtained  with  the  use  of  comparatively  small  diameters  of 
the  parts. 


188  GASOLINE  AUTOMOBILES 

The  type  of  disk  clutch  described  is  intended  for  dry  f ric- 
tional  surfaces.  Some  clutches  of  this  type  are  made  to 
operate  in  a  bath  of  oil,  so  that  in  their  disengaged  position 
the  surfaces  of  the  disks  are  partly  covered  with  oil.  When 
the  clutch  foot-pedal  is  released  and  the  springs  pull  the  disks 
together,  the  coating  of  oil  on  the  frictional  surfaces  is  gradu- 
ally squeezed  out.  The  oil  bath  makes  possible  a  very  gradual 
engagement  of  one  set  of  disks  on  the  other  so  as  to  avoid 
jerky  clutch  operation. 

Speed-change  Gear  Sets.  Transmissions.  When  an  auto- 
mobile engine  has  just  been  started  and  the  clutch  has  been 
released,  the  engine  must  be  run  relatively  fast  and  the  auto- 


FIG.  162.— Leverage  of  Gearing. 

mobile  slowly  to  avoid4 'stalling."  Gradually  the  speed  of 
the  automobile  should  be  increased  to  get  efficient,  quiet 
operation.  Such  speed  changes  suggest  the  use  of  gears. 
Some  may  have  difficulty  in  understanding  the  underlying 
principle  of  gearing,  so  that  a  practical  illustration  in  simplest 
terms  will  be  explained.  Fig.  162  shows  two  gear  wheels 
A  and  B  meshed  so  that  the  teeth  of  one  are  between  the  teeth 
of  the  other.  Obviously  in  this  position  they  must  turn 
together.  Every  time  a  tooth  on  the  driving  gear  B  advances 
by  rotation  on  its  shaft  the  width  of  one  tooth,  the  driven 
gear  A  in  contact  with  it  will  also  advance  one  tooth.  If 
both  gears  have  the  same  number  of  teeth  they  will  turn  at 
the  same  speed.  On  the  other  hand,  if  the  driving  (smaller) 


CLUTCHES,  TRANSMISSIONS,  AND  DIFFERENTIALS     180 

gear  has  ten  teeth  and  the  driven  gear  has  sixty  teeth,  the 
driving  gear  will  make  six  (60-^-10)  times  as  many  revolu- 
tions as  the  driven  (larger)  gear. 

The  above  explanation  applies  only  to  the  principle  of 
speed  changes,  but  force  or  "power"  changes  with  gears  in 
automobile  operation  are  equally  important.  A  portion  of 
each  of  the  gears  in  Fig.  162  is  drawn  with  shading  to  explain 
the  force  changes  occurring  with  speed  changes.  When  driving 
an  automobile,  one  changes  to  the  slowly  moving  gears  ("low 
gear")  to  get  larger  forces  at  the  wheel  for  heavy  pulling. 
In  this  "gear  change"  the  engine  continues  to  give  the  same 
horsepower  as  before,  but  the  forces  are  different.  These 
forces  and  speed  changes  may  be  explained  by  comparison 
with  a  lever  as  in  Fig.  163.  The  ratio  of  the  lengths  of  the 


FIG.  163. — Example  of  Leverage. 

lever  arms  on  each  side  of  the  point  of  support  F  is  six; 
(6-^1)  so  that  with  a  load  of  ten  pounds  at  the  right-hand 
end,  the  smallest  amount  of  load  in  excess  of  sixty  pounds 
will  overbalance  the  right-hand  end  and  in  the  resulting  move- 
ment this  end  will  move  six  times  as  far  as  the  left-hand 
end.  The  ratio  of  movement  (or  speed)  is  therefore,  the 
exact  opposite  (inverse)  of  the  ratio  of  weights.  Similarly, 
a  gear  rotating  one-sixth  as  fast  as  its  driver  has  six  times 
as  much  turning  force  at  its  shaft.  In  other  words,  if  the 
gear  in  Fig.  162  with  radius  R^^  is  six  times  as  large  as  the 
one  with  radius  R2,  it  turns  only  one-sixth  as  fast,  but  has 
six  times  as  much  turning,  pulling  or  pushing  force  at  its 
shaft.* 


*  This  idea  of  increased  tractive  pulling  power  at  low  speed  over 
that  at  high  must  not  be  confused  with  the  previous  statement  that 
gasoline  automobile  engines  have  very  little  power  at  very  low  speed? 
as  shown  by  the  "stalling."  Very  low  speed  in  this  Connection  mean* 


190 


GASOLINE  AUTOMOBILES 


There  are  three  general  types  of  speed-change  gear  sets: 
(1)  Selective  sliding  gears,  which  are  arranged  so  that  any 
of  the  speeds  can  be  selected  at  will.  (2)  Progressive  sliding 
gears,  which  do  not  permit  selection  of  speeds  at  random,  but 
the  speed  changes  must  be  in  a  definite  order  or  in  succession, 
that  is,  one  cannot  for  a  three-speed  gear  move  the  gear 
shifting  lever  out  of  the  position  for  high  speed,  put  it  into 
"neutral"  position,  and  then  immediately  into  the  low-speed 
position.  When  using  this  kind  of  speed-change  gears,  it  is 
necessary  to  actually  put  in  contact  the  gears  of  the  inter- 
mediate speed  before  low-speed  gears  can  be  put  together. 
(3)  Planetary  gears,  which  are  a  combination  of  a  clutch 
and  a  simplified  sliding  gear  set.  The  first  and  third  arrange- 
ments are  most  used. 

Selective  Sliding  Gear  Type.  Fig.  164  shows,  somewhat 
simplified  as  to  details,  a  speed-change  gear  set  of  the  selective 


FIG.  164. — Direct  Drive  on 
Selective  Sliding  Gears. 


FiQ.  165. — Low-speed  Gearing. 


kind  arranged  for  sliding  operation.  Two  shafts  8  and  T  are 
shown  in  this  figure.  The  left-hand  end  of  the  shaft  8  is 
rigidly  connected  to  the  clutch  and  therefore  rotates  normally 
at  engine  speed.  This  shaft  as  shown  here  is  not  continuous 
but  is  really  two  separate  shafts  which  meet  end  to  end  and 
are  coupled  together.  The  two  shafts  can  be  separated  as 
shown  by  dotted  lines  in  Fig.  165.  When  the  shaft  8Z  is 
coupled  to  Sj,  as  in  Fig.  164,  both  shafts  will  rotate  at  engine 


that  the  power  strokes,  although  powerful,  are  so  far  apart  that  there 
is  not  sufficient  carrying  power  from  one  power  stroke  to  the  next,  and 
as  a  result  the  engine  stops. 


CLUTCHES,  TRANSMISSIONS,  AND  DIFFERENTIALS     191 

speed.  This  is  called  direct  drive  or  high  speed.  In  either 
position  of  S2,  however,  the  gear  wheel  A  on  ^x  is  meshed  with 
the  gear  wheel  B,  which  moves  the  shaft  T. 

When  the  automobile  is  to  be  operated  at  lowest  speed, 
the  gear  wheels  A,  B,  C,  and  D  are  used.  Since  the  gear 
wheel  B  is  always  in  mesh  with  the  gear  wheel  A  on  the 
shaft  $!  the  shaft  T  is  always  rotating  when  the  engine  is 
running.  On  the  shaft  S2  is  a  gear  wheel  D  which  is  free 
to  slide  on  its  shaft.  When  the  shafts  Si  and  82  are  discon- 
nected, if  by  some  method  or  device  the  gear  wheel  D  is  made 
to  slide  into  contact  or  mesh  with  the  gear  wheel  C  opposite 
on  the  shaft  T,  the  shaft  S2  will  be  driven  through  the  four 
gear  wheels  A,  B,  C,  D.  The  engine  shaft  S^  will  then  rotate 
much  faster  than  the  shaft  S2.  Difference  in  the  sizes  of  the 
gear  wheels  makes  this  speed  change.  Suppose  A  has  half 
as  many  teeth  as  B,  and  that  C  has  half  as  many  as  D.  Then 
the  shaft  T  will  rotate  half  as  fast  as  8t ;  and  the  shaft  S2 
will  rotate  half  as  fast  as  T,  or  one-fourth  as  fast  as  Slt  which 
is  a  satisfactory  speed  reduction  for  low-speed  gears  as 
actually  used  in  automobiles.* 

An  intermediate  speed  between  direct  drive  (engine  speed) 
and  low  speed  can  be  obtained  very  simply  by  providing,  in 
addition,  a  sliding  gear  wheel  E  on  the  shaft  T  and  a  stationary 
gear  wheel  F  on  the  shaft  S2.  When  E  and  F  are  meshed  and 
C  and  D  are  out  of  mesh,  the  shaft  T  will  rotate  at  half  the 
speed  of  the  shaft  Sl ;  and  if  E  and  F  have  the  same  number 
of  teeth,  the  shaft  82  will  rotate  also  at  half  the  speed  of  8^ 

For  reverse  speed,  the  gearing  arrangement  is  shown 
diagrammatically  in  Fig  166.  An  auxiliary  gear  wheel  R 
on  a  short  shaft  U  is  made  to  mesh  with  another  sliding  gear 
wheel  K  on  the  shaft  T.  This  is  not  a  practical  case,  but 
in  a  simple  way  shows  the  principle.  The  directions  of  rota- 
tion of  the  shafts  8lf  T,  U  and  S2  are  shown  clearly  by  arrows 
in  the  figure.  As  the  gears  were  arranged  in  Figs.  164  and 


*  Sliding  speed -change   gears   are   really  only  a  modification   of  the 
back-gearing  used  commonly  on  lathes  of  various  kinds. 


192 


GASOLINE  AUTOMOBILES 


165  the  shaft  S2  was  driven  anticlockwise  in  the  same  direc- 
tion as  $!,  while  its  rotation  in  Fig.  166  for  reverse  speed 
is  clockwise,  which  gives  a  backward  or  reverse  movement  of 
the  automobile. 

Fig.  167  shows  a  commercial  design  of  sliding  speed-change 
gears  somewhat  differently  arranged,  and  provision  is  made 
for  mechanically  shifting  the  gears  by  the  use  of  a  hand 
operating  lever  L,  shown  attached  to  a  joint  /  at  the  top  of 
the  gear  case.  The  letters  in  this  figure  correspond  to  those 
used  in  Figs.  164,  165,  and  166.  In  the  operation  of  shifting 
gears,  the  lever  L  moves  back  and  forth  so  that  the  short 
lever  or  "finger"  F  engages  with  the  shifting  forks  or  yokes 
H  and  J.  One  of  these  controls  the  low  speed,  and  the  other 


K. 
FIG.  166. — Reverse  Gearing. 

the  intermediate  speed  and  the  high-speed  gears.  In  order 
to  move  the  one  or  the  other  of  the  shifting  forks  or  yokes 
H  or  J  the  lever  L  can  be  moved  back  and  forth  through 
the  top  of  the  gear  box  by  swinging  on  the  joint  /.  The 
operator  of  the  automobile .  can  pass  directly  from  any  set 
of  gears  to  any  other ;  that  is,  he  can  select  any  gear  desired. 
For  this  reason  this  arrangement  is  called  the  selective  type 
to  distinguish  it  from  the  progressive  type  which  was  once 
commonly  used  on  automobiles,  but  is  now  only  used  on  motor- 
cycles. 

The  important  advantages  of  selective  speed-change  gears 
ire  that  the  gears  can  be  shifted  rapidly  and  the  gear  teeth 
are  less  likely  to  be  broken  off  or  "stripped"  than  in  the 
progressive  type.  Selective  gears  are  also  more  compact, 


CLUTCHES,  TRANSMISSIONS,  AND  DIFFERENTIALS     193 


making  possible  shorter  and  therefore,  stiffer  shafts  in  the 
gear  box. 

These  descriptions  of  sliding  gear  sets  have  referred  to 


_.....  Main  Shaft- -5Z 
Jo  Axle  Drive  Shaft- 

'-Drive  End 

^!:;* Lai/Shaft- 

^ForLowSpeed 
'•Forlni-ermedicrhe  Speed 
FIG.  167. — Typical  Speed-Change  Gears  or  Transmission. 

three  speeds  ahead  and   one  reverse.     Some  sets,  however, 
particularly  those  intended  for  very  high  speed  automobiles 


Neutral  Gear  Position 


Fig.  168. — Gear  Wheels  A  and  B  connected. 


are  supplied  with  gears  giving  four  speeds  ahead.  The  fourth 
speed  is  sometimes  arranged  to  drive  the  axle  drive  shaft 
corresponding  to  82  in  the  preceding  figures  faster  than  the 


194 


GASOLINE  A  UTOMOBILES 


engine  shaft  8lf  and  the  third  speed  is  direct  drive  at  engine 
speed.  There  are  some  automobiles  especially  when  designed 
for  continuously  high-speed  operation  which  have  the  third 
speed  on  gears  and  get  the  fourth  on  direct  drive.  It  seems 
to  be  the  best  practice,  however,  to  get  the  fourth  speed  by 


Low  Gear  Position 


FIG.  169. — Gear  Wheels  A,  B,  C,  and  D  Connected. 


the  suitable  use  of  gears  and  have  the  direct  drive  on  the 
third  speed.  All  gear  drives  are  more  noisy  than  direct  drive 
so  that  most  operators  prefer  direct  drive  on  the  speed  they 
intend  to  use  most. 


Intermediate  Gear  Position 


FIG.  170.— Gear  Wheels  'A,  B,  E,  and  F  Connected. 


The  teeth  of  sliding  gears  are  not  made  with  "square" 
or  right-angle  corners  as  in  ordinary  gears,  but  the  ends  of 
the  teeth  are  rounded  so  that  they  will  readily  fit  into  each 
other  when  they  are  to  be  meshed. 

Figs.  168-171  show  the  gear  positions  for  three  speeds  ahead 


CLUTCHES,  TRANSMISSIONS,  AND  DIFFERENTIALS     195 

and  neutral  in  a  typical  selective  sliding  gear  set.  In  the 
neutral  position  shown  in  the  first  of  the  figures,  the  gears 
A  and  B  are  the  only  ones  meshed  and  the  axle  drive  shaft 
$2  or  the  "main  drive  shaft"  is  idle. 


High  Gear  Position 


Fie.  171.— Shafts  8t  and  8,  Connected. 


Shifting1  Lever  for  Speed-change  Gears.  Fig.  172  shows 
the  positions  of  the  shifting  lever  on  the  speed-change  gears 
or  the  transmission  as  operated  on  automobiles  with  the 


Reve 


termediate 


FIG.  172. — Usual  Type  of  Gear  Shifting  Lever. 

usual  type  of  selective  sliding  gears  as  shown  in  Figs.  167 
and  168.  The  usual  position  of  the  shifting  lever  and  speed- 
change  gears  with  respect  to  the  engine  is  shown  in  Fig.  173. 
Dodge  Automobile  Speed-change  Gears.  In  the  speed- 
change  gears  described  the  method  of  continuously  driving 


196 


GASOLINE  AUTOMOBILES 


the  counter  shaft  S2  has  been  used,  and  this  is  the  general 
practice.     A  notable  exception  is  in  the  Dodge  automobile 

Detachable  CylimkrHead 


Exhaust  Hani  fold 


Univtrsal  Joint  .- 
Transmission  Countershaft 


Ctu** 


FIG.  173. — Automobile  Engine  and  Speed-change  Gears. 
Direct  Drive  -. 


Flywheel" 


Spring  Plates        •         i  Emergency  Brake Levtr 
•'  —  '  -  tr+  -  Speed  Change  Layer 

Ma  in  Shaft- 


UniYtrsatJoi'rrf 
DriveSftaft 


Countershaft        StirftGear 
Drive  6ear 

FIG.  174. — Dodge  Speed-change  Gears  or  Transmission. 

in  which  the  counter  shaft  as  shown  in  Fig.  174,  is  put  out  of 
engagement  with  its  gear  connections  when  the  connection  is 


CLUTCHES,  TRANSMISSIONS,  AND  DIFFERENTIALS     197 

made  for  direct  drive.     Fig.  175  shows  the  shifting  lever  for 
the  speed-change  gears  on  this  type  of  automobile. 


VVIntermediate 


R 
FIG.  175. — Gear-shifting  Lever  on  Dodge  Automobiles. 

Planetary  Gear  Transmission.  In  distinction  from  the 
sliding-gear  types  described  there  is  another  important  kind 
of  speed-change  gears  which  is  not  shifted  in  or  out  of  mesh 
for  the  different  speeds ;  but  is  always  in  mesh.  This  kind 


Jup/f'or 


Venus 


Mars- 


Earth 


FIG.  176.— Planetary  Gear  Wheels. 

is  called  a  planetary  gear  or  planetary  transmission,  because 
of  a  fancied  resemblance  of  the  movements  of  its  small  and 
large  gear  wheels  to  the  revolution  of  the  planets  around  the 
sun  (Fig.  176). 

This  device  is  complicated  when  all  its  parts  are  assembled 
so  that  a  description  will  first  be  given  of  a  relatively  simple 


198 


GASOLINE  AUTOMOBILES 


example  of  planetary  gears  as  sometimes  used  on  machinery 
for  reversing  the  direction  of  rotation  of  a  shaft.  Fig.  177 
shows  a  diagram  of  such  gears.  The  central  gear  wheel  G 
is  attached  to  the  engine  crank  shaft  S,  over  which  is  loosely 
fitted  a  hollow  shaft  K.  A  larger  gear  wheel  /  with  teeth 
inside  the  rim  is  firmly  attached  to  the  shaft  K.  Either  shaft 
may  be  moved  independently  of  the  other — the  shaft  8  may 
turn  in  one  direction  and  the  shaft  K  in  the  reverse  direction ; 
or  they  may  rotate  at  different  speeds.  The  central  gear  wheel 
G  meshes  with  the  four  small  gear  wheels  marked  y  which 


BandBrake 


a 
FIG.  177. — Simple  Planetary  Transmission. 

are  supported  on  the  four  small  pins  marked  P,  which  are 
fastened  to  the  flat  surface  of  the  disk-plate  D.  A  circular 
band  a  (like  a  brake  band)  which  is  shown  heavily  shaded 
in  the  figure  can  be  tightened  by  pulling  on  the  rod  R, 
usually  by  means  of  a  foot  pedal.  When  this  band  is  tightened, 
it  grips  the  disk  plate  D  and  prevents  it  from  turning,  and 
the  four  pins  marked  P  are  held  stationary.  As  a  result  the 
four  small  gears  marked  g,  rotate  on  the  ''internal"  teeth 
of  the  large  gear  wheel  /  and  turn  it  in  the  opposite  direction 
to  the  rotation  of  the  gear  wheel  G,  attached  to  the  shaft  8. 
The  gear  wheel  7  when  thus  rotated  turns  the  hollow  shaft 
K  in  the  opposite  or  reverse  direction  to  the  rotation  of  the 


CLUTCHES,  TRANSMISSIONS,  AND  DIFFERENTIALS     199 

shaft  8.  If  the  diameter  of  the  gear  wheel  G  is  one-half  the 
diameter  of  the  gear  wheel  /  the  shaft  K  will  rotate  at  half 
the  speed  of  8.  Thus  it  will  be  seen  this  set  of  planetary 
gears  not  only  gives  reversed  direction  but  also  speed 
reduction. 

Ford  Planetary  Speed-change  Gears.  An  assembled  view 
of  the  speed-change  gears  of  the  planetary  transmission  used 
in  Ford  automobiles  is  shown  in  Fig.  178,  and  the  respective 


Flywheel-... 


Triple.  Gear'" 

Triple  6eaf 
Pin-D 

Driven  Gear 
Slow  Speed  Gear 

Reverse  Gear-—- 
Reverse  Drum 


f  Clutch  Discs 
I  (Clutch  Disc  Drum 

,..-  Clutch  Disc  Push  ffing 


fIufc/7  Springs 


•-Clutch  Shift 
._Dr/ver  Gear 
Transmission 
\        Shaft 
'  Brake  Drum 


FIG.  178. — Ford  Planetary  Transmission. 


parts  are  shown  disconnected  in  Fig.  179.  The  engine  fly- 
wheel F  is  rigidly  attached  to  the  engine  crank  shaft  C.  Three 
steel  pins  D  are  fastened  to  the  flywheel.  A  gear  wheel  with 
three  sets  of  teeth  E,  F,  G  is  fitted  loosely  so  that  it  can 
turn  on  each  of  these  pins.  Another  gear  wheel  K  fits  over 
the  crank  shaft  C  and  meshes  with  the  "E"  teeth  of  each 
of  the  gears  on  the  pins  D.  The  number  of  teeth  on  K  is 
the  same  as  on  E.  There  is,  therefore,  no  speed  change 
through  these  gears,  as,  all  move  with  the  same  number  of 
revolutions.  The  gear  K  is  attached  to  the  hollow  shaft  N 


200 


GASOLINE  AUTOMOBILES 


which  fits  over  the  crank  shaft  C.  Another  hollow  shaft 
which  fits  over  the  shaft  N  is  made  with  a  gear  wheel  L  which 
meshes  with  the  "F"  teeth  of  the  gears  on  the  pins  D.  A 
gear  wheel  M  fits  loosely  on  the  hollow  shaft  0  and  meshes 
with  the  "G"  teeth  of  the  gears  on  the  pins  D.  There  are 
fewer  teeth  on  L  than  on  F,  so  that  the  gear  wheel  L  has 
more  revolutions  or  turns  faster  than  the  gear  wheels  on  the 
pins  D.  On  the  other  hand  there  are  more  teeth  on  M  than 


Triple  Gear. 
Driven 'Gear^ 
Reverse  Drum  and  dear.. 


F/ytvheef- 
FiG.  179. — Ford  Planetary  Transmission  Disconnected. 


*rakeDrurrr      ShwSpsed  Drum 
and6ear 


on  G,  so  that  the  gear  wheel  M  turns  slower  than  the  gears 
on  D. 

The  gear  wheel  K  is  attached  to  the  hollow  shaft  N  which 
turns  with  it,  as  well  as  also  the  disk  T.  Likewise  the  gear 
wheel  L  is  on  the  shaft  attached  to  the  drum  8,  and  the  gear 
wheel  M  is  attached  to  the  disk  R.  The  hollow  shaft  N  with 
its  attached  gear  wheel  K  and  disk  T  moves  freely  on  the 
crank  shaft  C.  Similarly  the  hollow  shaft  0  with  its  attached 
gear  wheel  L  and  disk  8  moves  freely  on  the  shaft  N.  The 
gear  wheel  M  with  its  attached  disk  R  moves  freely  on  the 
shaft  0,  when  all  parts  are  assembled  as  shown  in  Fig.  178. 
The  irregular  disk  V,  however,  is  rigidly  fastened  to  the  crank 
shaft  C  to  which  are  attached  the  alternate  plates  of  a  mul- 
tiple disk  clutch.  The  other  set  of  plates  of  this  clutch  is 
fastened  to  the  disk  T  which  in  turn  is  bolted  to  the  rear  axle 
drive  shaft. 

Brake  bands  are  arranged  to  fit  over  the  outside  surface 


CLUTCHES,  TRANSMISSIONS,  AND  DIFFERENTIALS     201 

(circumference)  of  the  disks  T,  S,  and  R.  When  these  brake 
bands  are  loose,  the  gear  wheels  on  the  pins  D  drive  the  disks 
T,  S,  and  R  at  different  speeds,  proportional  to  the  number 
of  teeth  on  the  engaged  gears. 

High-speed  drive  is  simplest  to  explain,  as  all  the  brake 
bands  are  loose.  The  multiple-disk  clutch  is  engaged  by 
pushing  the  clutch  hand  lever  forward.  The  clutch  plates 
on  the  irregular  disk  V  attached  to  the  crank  shaft  engage 
with  the  clutch  plates  on  the  disk  T,  which  is  permanently 
fastened  to  the  axle  drive  shaft.  Engaging  the  clutch  plates 
makes,  therefore,  a  direct  drive  between  the  engine  crank 
shaft  C  and  the  axle  drive  shaft.  The  entire  planetary 
mechanism  is  locked  together  and  turns  at  the  same  speed 
and  in  the  same  direction  as  the  engine  crank  shaft. 

Low-speed  drive  is  obtained  by  tightening  the  brake  band 
on  the  disk  S  by  pushing  the  clutch  foot  pedal  forward.  Then 
the  disk  8  and  the  attached  gear  wheel  L  (on  the  hollow 
shaft  0)  are  held  stationary.  But  since  gear  wheel  L  is 
meshed  with  the  "F"  teeth  of  the  gears  on  the  pins  D,  the 
rotation  of  the  flywheel  will  make  these  gears  rotate  on  the 
pins.  Because  of  the  smaller  number  of  teeth  on  L  than  on 
F  the  gears  on  the  pins  D  will  not  make  as  many  revolutions 
as  the  flywheel,  actually  they  turn  at  almost  exactly  two- 
thirds  the  engine  speed,  and  in  the  same  direction  as  the 
flywheel.  In  practical  effect,  this  means  that  with  respect 
to  the  rotation  of  the  flywheel,  the  gears  on  the  pins  D  have 
turned  backward  one-third  of  a  revolution  during  each  revolu- 
tion of  the  flywheel.  The  "E"  teeth  on  these  gears  are 
meshed  with  the  gear  wheel  K  and  both  have  the  same  number 
of  teeth.  Turning  back  the  "F"  and  "E"  teeth  one-third 
of  a  revolution,  as  explained,  turns  the  gear  wheel  K  the 
same  part  of  a  revolution  ahead,  with  respect  to  the  rotation 
of  the  flywheel.  It  is  a  general  principle  that  the  teeth  on 
any  two  meshing  gear  wheels  move  in  opposite  directions.  In 
every  revolution  of  the  flywheel,  therefore,  the  gear  K  will 
move  about  one-third  as  fast  as  the  flywheel  and  in  the  same 
direction.  The  axle  drive  shaft  will  also  be  driven  at  about 


202  GASOLINE  AUTOMOBILES 

one-third  engine  speed  and  in  the  same  direction,  because 
the  gear  wheel  K  is  fastened  to  the  hollow  shaft  N  on  the 
clutch  disk  T  which  moves  the  axle  drive  shaft,  the  same 
as  in  direct  drive. 

Reverse  drive  is  obtained  by  tightening  the  brake  band 
on  the  disk  R,  by  pushing  the  reverse  foot  pedal  forward.  At 
the  same  time  the  hand  lever  must  be  in  middle  position  or  the 
clutch  pedal  pressed  down  to  release  the  clutch.  The 
disk  R  and  the  attached  gear  wheel  M  are  then  held  stationary. 
The  gear  wheel  M  is  meshed  with  the  "G"  teeth  of  the  gears 
on  the  pins  D,  but  the  number  of  teeth  meshed  on  the  pins 
D  is  now  less  than  on  the  connected  gear  wheel.  With  this 
gear  arrangement  the  teeth  "G"  are  turned  through  about 
one  and  a  quarter  revolutions  for  each  revolution  of  the 
flywheel,  which  means  that  the  teeth  "G"  and  also  the  teeth 
"E"  are  moved  ahead  of  the  flywheel  one-quarter  of  a  revolu- 
tion for  each  revolution  of  the  flywheel.  Since  the  number 
of  teeth  on  E  and  K  is  the  same,  the  net  result  of  these  gear 
movements  is  that  the  gear  wheel  K  with  its  attached  shaft 
N,  the  clutch  disk  T,  and  the  axle  drive  shaft  are  driven 
at  about  one-fourth  the  engine  speed  in  the  opposite  or  reverse 
direction  to  the  engine  rotation. 

This  device  gives  only  two  forward  speeds  (low-speed  and 
high-speed)  and  reverse,  and  is  considered  suitable  only  for 
use  on  light  automobiles  like  those  of  the  Ford  make. 

The  brake  on  this  kind  of  transmission  is  a  band  on  the 
brake  drum  (Fig.  178)  on  the  outside  of  the  end  driving  plate. 
The  foot  pedal  is  in  the  position  nearest  the  driver's  seat. 

Summary.  The  Ford  planetary  transmission  is  operated 
by  the  back  and  forth  movement  of  a  foot  pedal.  For  slow- 
speed  operation  the  foot  pedal  is  in  the  position  farthest  from 
the  driver's  seat,  when  the  gripping  strap  is  on  the  middle 
drum  and  holds  it  stationary.  This  makes  the  triple  gears 
rotate  on  their  shafts  as  the  flywheel  rotates.  This  rotation 
of  the  gears  drives  the  gear  K  (Fig.  179)  and  with  it  the  drive 
shaft  slowly  forward,  because  of  the  difference  in  the  size  of 
the  gears. 


CLUTCHES,  TRANSMISSIONS,  AND  DIFFERENTIALS      203 

For  reverse  operation  the  reverse  foot  pedal  is  pushed  to  its 
extreme  position  toward  the  engine  and  the  end  drum  R  is 
gripped.  This  makes  the  triple  gears  rotate  on  their  shafts  as 
the  flywheel  rotates,  but  since  the  reverse  gear  is  larger  than 
the  driven  gear,  the  motion  of  the  triple  gears  drives  the  gear 
K  slowly  backward. 

For  high  speed  the  foot  pedal  is  in  its  back  position  and 
the  whole  mechanism  is  gripped  together  and  rotates  at  the 
speed  of  the  engine. 

Steering  Gears  and  Front  Axles.  Practically  all  auto- 
mobiles are  steered  or  given  direction  by  some  means  of  turn- 


FlQ.  180. — Steering  Column. 

ing  the  front  wheels  without  turning  the  whole  front  axle. 
Steering  is  done  by  a  steering  wheel,  attached  to  a  steering 
column  (Fig.  180),  which  transmits  the  movement  of  the 
wheel  through  a  screw  or  worm  gear  to  a  system  of  levers  and 
rods  as  shown  (Fig.  182)  to  the  steering  knuckles  K,  one  sup- 
porting each  front  wheel.  Each  front  wheel  is  attached  to  the 
knuckle  spindle  (Fig.  181)  supported  on  roller  or  ball  bear- 
ings. At  the  lower  end  of  the  steering  column  is  the  arm  L 


204 


GASOLINE  AUTOMOBILES 


(Fig.  182)'.  From  this  arm,  motion  is  transmitted  to  the  short 
arm  K  on  the  steering  knuckle  by  means  of  the  drag  link  D 
which  moves  directly  the  front  wheel  of  the  automobile  on 


w 


FIG.  181.— Steering  Knuckle. 

the  driver's  side.  The  other  wheel  is  moved  by  the  tie  rod  R 
(sometimes  called  transverse  drag  link).  The  steering 
knuckles  are  fastened  to  the  front  axle  by  hinged  connections 


FlG.  182.  —  Steering  Gear  and  Front  Axle. 

on  king  bolts,  so  that  the  front  wheels  are  free  to  swing 
through  nearly  a  quarter  circle  about  the  king  bolt  as  a  center. 
This  gives  the  wheels  the  necessary  turning  movement  in 
steering. 


CLUTCHES,  TRANSMISSIONS,  AND  DIFFERENTIALS    205 

Fig.  180  shows  the  essential  parts  of  a  typical  well-made 
steering  gear.  Inside  the  steering  column  is  the  steering  tube; 
the  upper  end  is  connected  to  the  steering  wheel  H  and  the 
lower  end  to  a  worm  gear  W.  When  the  steering  wheel  is 
turned  it  moves  the  steering  tube  and  the  worm  gear  at  its  end 
in  the  same  direction.  The  gear  segment  G  meshing  with  the 
worm  gear  turns  the  attached  arm  L  (Fig.  182)  or  steering 
lever  so  that  it  pulls  or  pushes  on  the  drag  link  D,  and 
indirectly  on  the  tie-rod  R.  The  drag  link  and  the  tie-rod 
move  the  steering  knuckles  on  the  front  wheels. 

A  worm  gear  is  an  ideal  device  for  steering  gears  as  it  is 
non-reversible.  While  the  slightest  movement  of  the  steering 
wheel  is  readily  transmitted  by  this  device  to  the  front  wheels, 
the  up  and  down  movement  and  jarring  of  the  front  wheels 
on  rough  roads  cannot  appreciably  jar  or  turn  the  steering 
wheel.  Inside  the  steering  tube  are  (1)  the  tnrottle  rod  B, 
going  to  the  carbureter  and  (2)  the  spark  control  rod  A  con- 
nected to  the  ''timer"  which  is  the  device  for  regulating  the 
time  of  ignition  in  the  engine  cylinders.  These  two  rods 
within  the  rim  of  the  steering  wheel  are  turned  by  the  levers 
T  and  8.  The  spark  lever  S  is  attached  to  the  rod  A  at  the 
center  of  the  column  and  operates  the  small  short  rod  A  at 
the  lower  end.  The  throttle  lever  T  is  attached  to  the  tube  B 
and  operates  the  short  tube  B.  A  foot  lever,  called  an  accel- 
erator, is  connected  in  most  automobiles  to  the  rods  between  the 
short  tube  B  on  the  steering  column  and  the  short  lever  on  the 
throttle  valve  of  the  carbureter. 

The  front  axle  of  an  automobile,  unlike  in  an  ordinary 
wagon,  is  fastened  by  means  of  the  springs  to  the  frame  of 
the  automobile  and  does  not  turn.  The  front  wheels  are  not 
parallel,  but  foregather  slightly  so  that  if  the  lines  of  the 
wheels  are  projected  forward  far  enough,  they  would  meet 
and  make  a  pointed  effect,  like  the  bow  of  a  boat.  The  effect 
of  this  foregathering  is  to  bring  a  slight  but  constant  pressure 
upon  both  wheels  and  makes  them  less  likely  to  swerve  through 
contact  with  road  unevenness.  Also  the  wheels  undergather, 
called  camber,  so  that  the  load  is  thus  brought  over  the  center 


206  GASOLINE  AUTOMOBILES 

of  support  of  each  knuckle  so  as  to  minimize  the  bending 
stresses,  as  shown  in  Fig.  181.  This  deviation  of  the  wheels 
produces  a  slight  wear  on  the  tires,  but  is  more  than  com- 
pensated by  the  advantages.  If  the  tie  rod  or  the  front  axle 
should  be  accidentally  bent  so  that  the  foregather  is  increased, 
there  would  be  excessive  wear  of  tires. 

Bear  Axles.  The  front  and  rear  axles  together  support 
the  weight  of  the  automobile.  The  front  axle  with  its  steer- 
ing gear  and  links  serves  for  steering,  and  the  rear  axle 
with  its  gears  transmit  the  power  of  the  engine  to  the  wheels. 
When  the  axle  is  stationary  and  is  held  firmly  in  place  like 
in  a  horse-drawn  wagon,  an  automobile  trailer,  or  some 
kinds  of  trucks  with  chain  drives,  there  is  no  special 
mechanism  necessary  on  the  rear  axles  as  the  wheels  are 
free  to  turn  on  the  ends  of  the  axles.  Such  axles  are  called 
"dead"  axles.  With  this  kind  of  wheel  equipment  there  is 
no  difficulty  in  going  around  turns  as  each  wheel  is  adjustable 
to  its  own  speed.  In  modern  automobiles,  however,  the  two 
rear  wheels  are  rigidly  fastened  to  the  rear  axle  which  is 
set  in  bearings  so  that  it  can  rotate  with  the  wheels.  Such 
a  wheel  and  axle  arrangement  is  called  a  "live"  axle.  If  this 
axle  were  made  continuous,  in  one  piece,  the  wheels  could 
only  move  together  and  with  the  axle,  so  that  in  going  around 
a  sharp  curve,  if  the  wheel  on  the  outside  of  the  curve  moved 
normally,  the  one  on  the  inside  would  have  to  move  at  the 
same  speed  on  account  of  their  connection  together  and  must 
therefore  slip  on  the  ground. 

At  every  turn  in  the  road  there  would  be  some  slipping, 
and  at  every  sharp  turn  there  would  be  very  much  slipping 
with  excessive  wear  on  tires.  Besides  the  automobile  would 
not  steer  easily  when  making  turns.  It  would  be  something 
like  running  an  automobile  with  a  brake  set  on  only  one  wheel. 
On  account  of  these  difficulties  it  is  obvious  that  some  device 
must  be  used  to  make  possible  separate  and  independent 
movement  of  the  two  rear  wheels  and  still  permit  the  rigid 
fastening  of  the  wheels  to  the  axle  so  that  it  can  be  used 
to  transmit  the  driving  power  of  the  engine  to  the  wheels. 


CLUTCHES,  TRANSMISSIONS,  AND  DIFFERENTIALS     207 

Differential  Gears.  Gears  for  driving  a  divided  rear  axle 
are  shown  enlarged  in  Fig.  183.  At  the  end  of  the  axle  drive 
shaft  8  is  a  pair  of  bevel  gears*  B  and  C,  one  of  these  gears 
(<7),  meshes  with  the  side  of  the  larger  gear  (B).  Two  other 
gears  D  and  E  are  firmly  attached  respectively  to  the  axles  At 
and  A2  and  these  in  turn  are  attached  to  the  wheels.  An  inter- 


FiG.  183.  —  Simple  Example  of  Differential  Gears. 

mediate  bevel  gear  on  the  shafts  connecting  D  and  E,  is  sup- 
ported on  the  frame  F. 

If,  now,  each  of  the  axles  Al  and  A2  offers  the  same 
resistance  to  turning,  both  will  rotate  at  the  same  speed. 
If,  again,  the  automobile  is  making  a  sharp  turn  to  the  right, 
so  that  the  left-hand  wheel  has  the  longer  distance  to  go, 
the  right-hand  wheel  resists  going  as  fast,  and  the  intermediate 
bevel  gears  D  and  E  will  roll  slightly  on  the  bevel  gear  F  which 
is  on  the  short  shaft  s.  The  right-hand  wheel  will  conse- 
quently turn  at  a  slower  speed. 

There  is  another  interesting  case  to  study.  If  the  right- 
hand  wheel  is  lifted  from  the  ground  as  one  does  when 
changing  tires,  and  the  engine  is  started  and  put  "into  gear" 


*  Bevel  gears  serve  the  same  purpose  as  ordinary  (spur)  gear  wheels. 
The  teeth  must  be  made  on  an  angle  instead  of  on  the  periphery  so  that 
they  can  mesh  at  an  angle. 


208  GASOLINE  AUTOMOBILES 

so  as  to  drive  the  rear  axle  and  wheels,  the  right-hand  wheel 
will  spin  around  in  lively  fashion  but  the  left-hand  wheel 
on  the  ground  will  not  move.  This  is  exactly  what  happens 
when  one  rear  wheel  is  in  soft  mud  without  chains  on  the 
tire  (without  resistance),  and  the  other  wheel  is  on  firm 
ground.  The  slipping  wheel  will  spin  in  the  mud  but  the 
one  on  firm  ground  will  not  move. 

As  rear  axle  differential  gears  are  actually  made  there 
are  usually  three  or  four  of  the  intermediate  bevel  gears 
like  gear  F,  called  the  differential  gears,  and  they  are  made 
much  smaller  relatively  than  those  marked  in  Fig.  184.  All 


Differential  Gears 

Driving  .Gears      \  ^^     Axle  Shaft  No >J 

jSearffal 


Driven  Gear  ^     s^S^p^m^i...  QearNo.2 

\le  Shaft Ho.£ 
FIG.  184.— Differential  Gears. 

of  these  gears  are  supported  in  a  small,  compact  case  which  is 
built  up  as  a  part  of  the  main  casing  or  housing  which  is 
really  included  in  one  continuous  axle  and  differential 
casing  somewhat  as  shown  in  Fig.  185.  The  bevel  gear 
on  the  end  of  the  axle  shaft  is  shown  inside  the  main 
casing  or  housing  which  includes  also  the  axle  tubes.  Inside 
the  axle  tubes  are  the  bearings  (roller  or  ball  types)  both 
for  supporting  the  differential  gearing  and  the  axles. 

Extending  from  the  differential  housing  toward  the  engine 
is  a  casing  similar  to  that  for  the  axles  for  the  protection 
of  the  axle  shaft,  and  in  this  casing  are  roller  or  ball  bearings 
for  supporting  this  shaft  with  minimum  friction. 

Automobile  axles  that  are  to  go  into  the  bevel  gears 
are  usually  made  with  square  or  else  with  ribbed  ends 


CLUTCHES,  TRANSMISSIONS,  AND  DIFFERENTIALS     209 

to  slip  into  similarly  shaped  openings  in  the  hubs  of 
these  gears.  The  method  of  attaching  the  wheel  ends  of  the 
axles  determines  the  type  of  axle  construction. 


FlG.  185. — Casing  or  Housing  of  Differential  Gears, 
Kear  Axle,  and  Roller  Bearings. 

Fig.  186  shows  very  clearly  the  differential  gears,  differ- 
ential axle,  axle  shaft  casings,  roller  bearings  and  wheel  con- 


Fio.  186.— Parts  of  Standard  Type  of  Rear  Axle 
Differential  Gears. 


struction  of  a  Ford  rear  axle.     The  small  differential  gears 
«!,  s2,  s3,  are  very  clearly  shown. 

Types  of  Differential  Drives.    There  are  several  approved 
methods  of  transferring  the  power  from  the  axle  drive  shaft 


210  GASOLINE  AUTOMOBILES 

to  the  differential  gears  in  the  rear  axle.     Ordinary  bevel, 
spiral-bevel,  and  worm  gears  are  most  used. 

Fig.  187  shows  the  standard  type  of  ordinary  bevel  gear 
drive.  Roller  bearings  are  used  for  all  bearing  surfaces.  Bevel 
gears  always  produce  an  end  thrust,  caused  by  the  inclination 
of  the  teeth  and  this  thrust  tends  to  separate  the  gears;  for 
this  reason  the  conical  roller  bearings  shown  have  an  ad- 
vantage. If  straight  roller  or  ball  bearings  were  used  special 
thrust  bearings  would  have  to  be  provided. 


FIG.  187.— Differential  Gear  Showing  Boiler  Bearings. 

In  a  spiral-bevel  gear  the  teeth  of  both  gear  wheels  are  cut 
so  as  to  be  of  the  same  spiral  shape.  A  gear  of  this  type  with 
spiral  cut  teeth  will  give  more  even  and  more  continuous 
driving  power  and  overcome  to  some  extent  the  larger  thrust 
or  ordinary  bevel  gears,  as  well  as  being  stronger. 

Worm  drives  are  used  mostly  for  large  and  heavy  trucks 
where  there  is  a  very  large  reduction  of  speed.  Unless  very 
carefully  made  the  friction  of  such  gears  is  excessive;  and 
in  any  case,  lubrication  must  be  given  careful  attention.  For 
this  reason  they  are  not  much  used  on  pleasure  cars. 


CLUTCHES,  TRANSMISSIONS,  AND  DIFFERENTIALS     211 

Types  of  Rear  Axles.  There  are  two  kinds  of  rear  axles 
for  vehicles  in  general.  The  so-called  "dead"  axle  as  used 
on  wagons,  trailers  and  for  some  chain  drive  trucks  where 
the  axle  does  not  rotate  has  already  been  mentioned.  The 
other  kind  of  this  general  classification  refers  of  course  to 
those  having  a  rotating  "live"  axle  for  transmitting  power 
through  gearing  at  the  middle  of  the  axle.  Live  axles  are 
sub-divided  into  a  further  classification  according  to  the 
method  of  construction,  particularly  as  to  the  attachment  and 
driving  of  the  wheels,  as  follows: 

Simple  live  rear  axle  is  well  illustrated  by  the  Ford 
rear  axle  shown  in  Fig.  188.  It  has  two  distinctive  services : 


Q-T1" 


FIG.  188. — Simple  Live  Bear  Axle    (Ford   Type). 


(1)  to  carry  the  weight  of  the  rear  of  the  car  (on  the  axles), 
and  (2)  to  transmit  the  power  from  the  axle  drive  shaft 
to  the  wheels.  The  wheels  are  securely  fastened  to  the  axles. 
Because  all  the  weight  of  the  automobile,  supported  on  the 
rear  springs,  is  carried  by  the  roller  bearings  shown  directly 
on  the  "live"  axles  at  the  wheel  a  broken  shaft  is  likely 
to  let  a  wheel  pull  itself  out  of  the  wheel  casing  and  let  down 
one  side  of  the  automobile.  This  is  a  disadvantage,  which 
is  not,  however,  so  serious  for  a  light  as  for  a  heavy 
automobile. 

Semi-floating  rear  axles  (Fig.  189)  have  the  bearings 
at  the  wheels  carried  on  an  extension  of  the  differential 
casing  or  housing.  This  type  is  an  improvement  over  the 
simple  live  axle  to  the  extent  that  the  load  is  not  put 


212 


GASOLINE  AUTOMOBILES 


directly  on  the  axle ;  but  there  is  in  this  type  also  the  danger 
of  a  wheel  running-  off  with  a  part  of  a  broken  axle  and 


FIG.  189.— Semi-floating  Axle. 


letting  down  the  automobile.  The  removal  of  stress  on  the 
axle  in  this  type  merely  makes  the  axle  a  little  less  liable  to 
break. 


FIG.  190. — Three-quarter  Floating  Axle. 


Three-quarter  floating  rear  axles  differ  from  the  semi- 
floating  type  essentially   in   the   method  of  supporting  the 


CLUTCHES,  TRANSMISSIONS,  AND  DIFFERENTIALS     213 

weight  at  the  wheel  end  of  the  axle.  Fig.  190  shows  details 
clearly  as  to  supporting  bearings.  This  type  has  the  ad- 
vantage over  the  two  types  already  explained  in  that  all 
bending  stress  is  removed  from  the  axle  and  all  the  load 
at  the  wheel  end  of  the  axle  is  carried  by  the  bearing  located 
in  the  body  of  the  wheel  directly  over  the  spokes.  It  has 
the  disadvantage,  however,  of  the  other  types  mentioned  in 
that  if  the  axle  breaks,  the  wheel  may  come  off.  This  danger 
is  fully  prevented  only  in  a  so-called  full-floating  con- 
struction. 

Full-floating  rear  axles  are  made  with  double  roller  or 
double  ball  bearings  on  the  wheel  end  of  the  axle   (Figs. 


FIG.  191.— Full-floating  Axle. 


191  and  192)  which  are  made  in  such  a  way  that  the  wheel 
will  remain  on  the  axle  casing  even  if  the  axle  should  be 
broken.  The  shaft  receives  only  the  twisting  stresses  due 
to  transmitting  power  to  the  wheels.  Further,  the  shaft 
can  be  taken  out  of  the  shaft  casing  and  replaced  by  merely 
taking  off  the  wheel  cap  at  the  hub.  At  the  wheel  end  the 
shaft  is  keyed  into  the  hub  cap.  Another  construction  is 
to  have  the  axle  made  with  a  squared  or  ribbed  end  to  fit 
an  opening  of  corresponding  shape  in  the  hub  cap.  Some- 
times the  outer  end  of  the  shaft  is  made  with  a  toothed 
or  "jaw"  clutch  which  fits  into  corresponding  recesses  in 
the  hub  cap.  This  latter  construction  permits  a  little  "lost 


214 


GASOLINE  AUTOMOBILES 


motion"  at  the  point  of  axle  attachment  and  relieves  the 
shaft  from  possible  distortion  which  might  be  caused  by 
a  bent  axle  casing. 


FIG.  192.— Full-floating  Axle. 


Universal  Joints.  The  axle  drive  shaft  cannot  run 
straight  from  the  change  gear  set  (transmission)  to  the  gears 
in  the  rear  axle  where  the  engine  power  is  applied  because 
the  gears  in  the  rear  axle  (differential)  are  at  a  much  lower 
level.  The  engine  shaft  runs  parallel  to  the  frame  of  the 
car  to  the  change  gear  set ;  but  from  that  point  the  driving 
shaft  slopes  downward  toward  the  rear.  Further,  the 
change  gear  set  is  bolted  firmly  to  the  frame  of  the  auto- 
mobile and  the  rear  axle  is  free  to  move  with  the  giving 
of  the  springs,  making  a  rigidly  constructed  shaft  between 
the  change  gear  casing  and  the  differential  gears  imprac- 
tical. The  necessary  (1)  freedom  of  movement  and  (2)  change 
of  direction  of  the  axle  driving  shaft  are  secured  by  the  use 
of  universal  joints. 

A  universal  joint  of  typical  shape  is  shown  in  Fig.  193. 
It  consists  of  two  forked  members  or  yokes  F^  and  F2  which 
are  keyed  or  otherwise  rigidly  fastened  to  the  shaft  8t  and 
S2  to  be  joined  flexibly.  Between  the  forked  members  is 
bolted  a  block  in  shape  somewhat  resembling  a  Greek 
cross.  In  the  ends  of  the  arms  of  this  cross  are  threaded 


CLUTCHES,  TRANSMISSIONS,  AND  DIFFERENTIAL*     215 

holes  into  which  the  pins  P,  P,  P,  P,  are  screwed  to  fasten  the 
forked  members  to  the  arms  of  the  cross.  By  this  arrange- 
ment either  fork  with  its  attached  rod  can  be  made  to  swing 
like  on  a  hinge  around  the  pins  fastening  it  to  the  cross. 
This  kind  of  movement  of  the  two  forks  make  a  joint  which 
can  be  turned  in  any  direction — "universal"  in  direction. 
By  the  use  of  this  device  it  is  possible  to  bend  a  driving 
shaft  in  any  direction,  either  momentarily  or  permanently, 
and  use  it  for  the  efficient  transmission  of  power. 


FIG.  193.  —  Example  of  Universal  Joint. 


It  is  also  necessary  to  provide  for  the  horizontal  move- 
ment forward  or  backward  of  the  rear  axle.  This  is  cared 
for  by  providing  a  slip  joint  on  one  of  the  shafts  connected 
to  a  universal  joint  to  move  freely  back  and  forth  in  a 
splined  or  squared  hole  in  the  yoke  of  the  joint. 

It  is  the  best  practice  to  fit  the  axle  drive  shaft  of  an 
automobile  with  two  universal  joints,  one  at  each  end  of 
this  shaft.  One  reason  for  this  is  that  if  two  shafts  are 
connected  to  a  universal  joint,  and  the  driving  shaft  rotates 
at  a  constant  speed,  the  driven  shaft  will  rotate  at  a  rate 
which  will  be  constant  only  if  the  two  shafts  lie  in  one 
straight  line  but  will  vary  if  they  lie  at  an  angle.  This 
variation  will  fluctuate  four  times  to  a  revolution,  twice 
reaching  a  maximum  and  twice  a  minimum.  The  extent 
of  this  variation  will  be  proportional  to  the  angle  between 
the  shafts.  If,  however,  the  axis  of  the  driving  shaft  and 
of  the  driven  shaft  are  parallel,  and  the  driving  shaft  and 


216  GASOLINE  AUTOMOBILES 

J;he  driven  shaft  are  connected  by  an  intermediate  shaft 
fitted  with  a  universal  joint  at  each  end,  and  if  these  joints 
be  arranged  with  their  adjacent  yokes  in  the  same  plane, 
then  the  variations  in  speed  of  the  first  joint  will  be  exactly 
neutralized  by  the  similar  variation  of  the  second  joint,  and 
the  axle  drive  shaft  will  rotate  at  a  uniform  speed. 

It  is  obvious  that  the  tendency  of  a  single  universal 
joint  is  to  give  a  jerky  motion  to  the  automobile,  this  jerky 
motion  increasing  with  the  angle  through  which  the 
universal  joint  acts.  Therefore,  if  properly  installed,  an 
axle  driven  shaft  with  two  universal  joints  is  always  better 
than  one  with  only  one  universal  joint. 

Another  reason  for  the  use  of  two  universal  joints  is 
that  much  greater  range  of  action  is  permitted  between  the 
rear  axle  and  the  frame  which  carries  the  power  plant  and 
body.  This  allows  the  necessary  freedom  of  movement  of 
the  rear  axle  when  passing  over  uneven  road  surfaces,  with- 
out producing  excessive  stresses  which  are  unavoidable  when 
only  a  single  universal  joint  is  used.  This  explains  why 
the  single- joint  construction  is  not  much  used  except  in  light- 
weight automobiles. 

Some  automobiles  of  recent  design  have  the  engine  set  so 
that  the  shaft  tilts  downward  towards  the  back.  The  axle 
drive  shaft  runs  straight  from  the  transmission  to  the  normal 
position  of  the  differential.  This  is  said  to  be  a  straight-line 
drive. 

Fabric  universal  joints  which  have  been  adopted  by  several 
manufacturers  are  made  by  joining  the  ends  of  two  shafts  by 
means  of  circular  fabric  (cotton  and  rubber)  disks.  A  forged 
steel  spider  having  three  arms  is  welded  or  otherwise  fastened 
to  the  end  of  each  shaft.  The  circular  disks,  usually  three  in 
number,  are  placed  between  the  spiders.  Each  spider  is 
independently  bolted  to  the  disks  so  that  the  arms  of  one  come 
between  the  arms  of  the  other,  necessitating  six  holes  in  the 
disks.  The  arms  are  said  to  be  "staggered."  The  "give  and 
take"  of  the  disks  is  said  to  be  sufficient  to  supply  the  neces- 


CLUTCHES,  TRANSMISSIONS,  AND  DIFFERENTIALS     217 

sary  end  motion.  Advantages  claimed  for  this  type  of  joint 
are  that  it  does  not  require  lubrication  and  will  not  rattle. 

Torque  members.  Torque  means  twisting  effort.  A  simple 
illustration  of  twisting  effort  and  reaction  is  as  follows:  A 
person  stands  in  a  boat  on  water  and  twists  a  pole  held  on 
shore.  The  boat  tips  in  the  direction  opposite  to  the  twisting 
force.  To  produce  the  same  twist  on  the  shore  end  of  the 
pole  and  keep  the  boat  from  tipping  it  can  be  supported  to 
the  shore  or  lake  bottom.  The  condition  is  similar  to  the 
turning  force  of  the  drive  shaft  on  the  rear  axle.  The  engine  and 
body  are  supported  on  the  frame  which  rests  at  the  rear  end  on 
springs  attached  to  the  rear  axle.  The  engine  twists  the  drive 
shaft.  The  axle  and  wheels  rest  on  the  ground  and  the  frame  tips 
on  the  springs  just  as  the  boat  tipped.  For  best  results  the  frame 
and  axle  should  be  fastened  together  so  that  the  frame  cannot 
twist  but  can  work  up  and  down  as  the  springs  bend.  It  may 
be  said  that  the  springs  will  accomplish  this  and  so  they  do  to 
a  certain  extent.  The  sole  use  of  springs  to  take  up  this  twist 
is  very  common  and  will  be  spoken  of  later.  The  springs 
have  their  own  particular  work  to  do  and  may  be  made  smaller 
if  they  are  relieved  of  this  additional  strain  by  use  of  torque 
members,  rods,  or  tubes,  which  prevent  this  twisting  reaction. 

Radius  Rods.  In  addition  to  the  twisting  stress  there  is 
another  stress  developed  between  the  rear  axle  and  frame 
due  to  the  power  transmitted  to  the  rear  wheels.  This 
is  the  reaction  of  the  axle  to  the  driving  force.  This  stress 
may  be  resisted  by  the  springs  or  to  relieve  them,  radius  rods 
may  be  used.  If  the  rear  wheels  of  an  automobile  rested  on 
rollers,  free  to  turn,  there  would  be  no  forward  movement. 
If  the  wheels  rest  on  something  solid — something  that  can 
"push  back" — the  car  is  pushed  ahead  and  the  push  comes 
through  the  axle  to  the  frame  of  the  car.  One  cannot  row  a 
boat  unless  the  oar  locks  are  fastened  down.  The  oars  push 
the  row  locks  and  the  row  locks  push  the  boat.  Just  so  the 
wheels  push  the  axle  and  the  axle  pushes  the  car  ahead  or 
back.  Rods  transmitting  the  driving  force  and  fastened  to 


218  GASOLINE  AUTOMOBILES 

the  frame,  which  pivot  and  allow  the  axle  to  move  up  and 
down  on  a  radius  are  called  radius  rods. 

If  the  car  has  no  torque  members  or  radius  rods  it  is  said 
to  employ  the  Hotclikiss  metTiod  of  driving.  This  method  has 
come  into  wide  use.  The  springs  and  bolts  connecting  the 
automobile  frame  to  the  rear  axle  are  necessarily  stronger 
than  when  torque  and  radius  rods  are  used.  The  entire  stress 
of  driving  the  car  comes  through  the  front  ends  of  the  rear 
springs. 

Brakes.  Both  the  foot  brake  (service  brake]  and  hand 
brake  (emergency  brake]  usually  act  on  brake  drums  attached 
to  the  rear  wheels.  Many  cars  are,  however,  now  equipped 
with  the  hand  brake  acting  on  a  drum  on  the  drive  shaft 
directly  back  of  the  transmission.  This  is  called  a  trans- 
mission brake.  The  emergency  brake  is  mainly  used  to  hold 
the  automobile  at  a  standstill  after  it  has  been  stopped.  It 
should  always  be  set  when  the  car  is  not  moving. 

Brake  Drums.  A  rear  axle  is  usually  equipped  with 
service  and  emergency  brakes.  Brake  drums  are  made  out  of 
pressed  steel  and  shaped  like  large  round  box  covers  from  ten 
to  fifteen  inches  in  diameter  and  two  or  three  inches  deep. 
They  are  fastened  rigidly  to  each  rear  wheel.  Inside  and 
outside  of  the  edges  of  these  drums  are  circular  bands  of  steel 
faced  or  lined  with  asbestos  fabric  which  has  been  treated 
with  a  compound  and  baked.  These  bands  are  arranged  so  they 
may  be  expanded  or  contracted  to  bind  on  the  brake  drum. 
They  are  operated  by  levers,  and  rods  or  wire  cables  which 
are  moved  by  the  foot  pedal  or  hand  lever. 

Equalizers.  When  either  the  brake  pedal  is  depressed  or 
the  hand  lever  is  pulled  back,  the  corresponding  band  on  the 
brake  drum  of  each  rear  wheel  is  tightened.  If,  as  is  often 
the  ease,  a  device  is  used  to  make  each  brake  band  grip  the 
same  as  the  other,  that  device  is  called  the  brake  equalizer, 
sometimes  brake  differential.  It  may  be  only  a  simple  lever 
like  the  whipple-tree  of  a  wagon  or  it  may  consist  of  bevel 
gears. 


CLUTCHES,  TRANSMISSIONS,  AND  DIFFERENTIALS     219 

Adjustment  of  Brakes.  A  type  of  shaft  or  transmission 
brake  operated  by  the  hand  lever  has  replaced  one  of  the 
two  sets  of  rear  wheel  brakes  on  many  cars.  Springs  are 
combined  with  the  brake  band,  as  they  are  also  in  the  case  of 
rear  wheel  brakes,  so  that  when  the  lever  or  pedal  is  released 
the  band  will  separate  itself  from  the  brake  drum  an 
appreciable  distance.  Additional  springs  are  supplied  to  hold 
the  brake  pedal  and  the  hand  lever  in  a  non-engaged  position. 
A  ratchet  is  provided  to  hold  the  hand  lever  in  an  engaged 
position  unless  it  is  desired  to  release  it.  On  all  brakes  there 
are  provided  means  for  tightening  or  adjusting  the  rods  and 
bands. 

It  is  needless  to  emphasize  that  brakes  should  be  kept  in 
adjustment.  In  a  released  position  it  should  be  possible  to 
insert  a  small  saw  blade  or  case  knife  blade  between  the  brake 
band  and  drum  all  around.  Too  much  opening  interferes  with 
the  quick  action  of  the  brake.  If  the  brake  band  rubs  it  will 
overheat  and  burn  the  asbestos  facing. 

Brake  adjusting  screws  should  be  kept  oiled  as  well  as  all 
parts  of  the  brake  levers.  Road  water  and  water  used  in 
washing  the  car  rusts  the  brake  parts  quickly  and  adjusting 
screws  give  considerable  bother  if  they  become  rusty. 

Several  foreign  cars  have  adopted  front  wheel  brakes  which 
supplement  the  action  of  the  rear  wheel  brakes,  permitting  a 
quicker  stop. 

Operation  of  Brakes.  Brakes  should  never  be  applied 
quickly  when  the  car  is  moving  at  more  than  fifteen  or  twenty 
miles  on  a  slippery  road,  level  or  down  grade.  If  they  are 
the  car  will  skid  or  slide  and  cannot  be  steered.  Accidents 
are  continually  happening  due  to  this  cause.  Anti-skid  tire 
chains  offset  the  liability  to  danger  from  skidding,  but  are  not 
an  absolute  preventive. 

The  engine  is  a  very  effective  brake  when  thrown  into 
low  or  intermediate  speed.  If  other  brakes  fail,  or  to  help 
them  out,  shift  the  gears  into  low  speed  and  let  the  clutch 


220  GASOLINE  AUTOMOBILES 

back,  so  that  the  engine  is  in  gear.  If  more  braking  action  is 
needed  cut  off  the  ignition. 

On  a  long  hill  do  not  use  the  foot  brake  continually.  Long 
grades  should  be  descended  at  a  comparatively  slow  speed  and 
the  hand  or  emergency  brake  used  alternately  with  the  foot 
brake  so  that  neither  brake  will  become  overheated.  If  one 
brake  is  used  continually  in  going  down  a  mountain  road  or  a 
very  long  steep  hill,  or  if  the  hill  is  descended  at  a  high  speed 
the  brake  will  get  so  hot  that  the  brake  lining  will  be  injured. 

Perhaps  one  of  the  greatest  causes  of  brake  failure  is  oil. 
The  oil  which  gets  on  the  brakes  usually  works  through  the 
rear  axle  housing  from  the  differential  gears.  The  owner  may 
put  too  much  oil  in  the  differential  and  it  travels  along  the 
inside  of  the  axle  tube.  The  oil  works  over  the  wheel  bearing 
and  into  the  brake  drum.  It  will  often  be  noticed  that  the 
oil  collects  mostly  on  the  right-hand  brake.  This  is  because  the 
crown  on  the  road,  and  the  ditch  alongside  which  are  used  in 
passing  other  automobiles,  tilt  the  automobile  so  that  the 
right-hand  wheel  is  lower  than  the  left-hand  wheel. 

Shock  Absorbers.  Shock  absorbers  slow  up  the  movement 
of  the  springs.  They  operate  on  either  one  of  two  general 
principles ;  ( 1 )  the  springs  are  made  stiffer  by  the  addition  of 
supplementary  springs  or  (2)  the  movement  of  the  springs  is 
dampened  by  some  friction  or  compressed  air  device.  An 
automobile  often  rides  smoothly  on  roads  with  good  surfaces, 
yet  when  driven  over  rough  roads  at  moderately  high  or  high 
speeds  it  jounces  the  occupants  around  badly.  If  the  shock 
absorbers  only  stiffen  the  springs  the  car  will  ride  smoother 
on  the  rough  roads  but  will  ride  harder  on  good  roads. 

The  simplest  form  of  shock  absorber  is  a  small  rubber 
bumper  which  is  placed  so  as  to  come  between  the  frame  and 
the  axle  when  the  spring  has  been  considerably  compressed. 
A  common  type  is  a  supplementary  coil  spring  which  only 
stiffens  the  car  springs.  This  makes  it  possible  to  carry 
heavier  loads  and  ride  more  comfortably  over  rough  roads, 
yet  the  car  will  not  have  the  same  slow  spring  action  on  boule- 
vards. 


CLUTCHES,  TRANSMISSIONS,  AND  DIFFERENTIALS     221 

More  efficient  types  are  made  to  connect  the  axle  and 
frame  of  the  car  with  some  friction  or  compressed-air  device. 
With  the  compressed-air  shock  absorber  an  air-cylinder  shock 
absorber  and  piston  are  connected,  one  with  the  frame  and 
the  other  to  the  axle  of  the  car.  By  regulating  the  escape  of 
the  compressed  air  the  movement  of  the  spring  is  slowed  up  as 
is  necessary.  A  variation  of  this  principle  is  the  employment 
of  oil  instead  of  air. 

Another  type  employs  the  principle  of  two  levers,  one 
connected  to  the  axle  and  the  other  to  the  frame  of  the  car, 
turning  on  a  friction  pad.  The  friction  between  these  levers 
may  be  varied.  Still  another  type  permits  the  axle  to  deflect 
towards  the  frame  but  in  so  doing  winds  up  a  strap  which 
has  to  unwind  before  the  spring  comes  back  to  normal.  This 
last  type  is  called  a  "snubber"  shock  absorber. 

Automatic  Gear  Shifts.  Attempts  have  been  made  to 
eliminate  the  gear-shifting  lever  in  order  to  simplify  the 
driving  of  a  car.  One  method,  used  on  the  Owen  Magnetic 
automobile,  only  partially  accomplishes  this  but  is  very  dis- 
tinctive. On  this  car  there  are  only  two  change-speed  gears, 
one  forward  and  one  reverse.  When  the  gear  lever  is  placed 
in  ' '  forward ' '  the  different  speed  changes  are  made  by  simply 
moving  a  selector  lever  on  the  steering  wheel.  The  changes 
in  engine  and  car  speed  are  not  obtained  by  gears.  All  the 
power  of  the  engine  is  converted  into  electric  power  and  the 
car  is  driven  by  an  electric  motor  mounted  directly  behind  the 
engine  and  dynamo.  This  dynamo  is  what  converts  the  engine 
power  into  electricity.  Shifting  the  speed  lever  on  the  steer- 
ing wheel  controls  the  speed  of  the  driving  motor  by  changing 
the  brushes  which  supply  current  to  it. 

The  Sauer,  a  German  automobile  which  has  been  imported 
into  this  country,  has  done  away  with  the  gear-shift  lever. 
On  this  car  there  is  a  set  of  gears  and  the  desired  speed  or 
combination  of  gears  is  chosen  by  a  selecting  mechanism  in 
conjunction  with  the  clutch  pedal.  The  driver  may  set  the 
selector  lever  at  any  time.  Then  when  the  clutch  pedal  is 
depressed  the  gears  shift  automatically  into  the  combination 


222  GASOLINE  AUTOMOBILES 

selected.  There  is  also  a  magnetic  gear  shift  which  American 
automobile  engineers  have  used  experimentally  and  have 
adopted  on  some  automobiles.  The  gear  set  or  transmission  is 
retained,  as  with  the  Sauer,  and  the  desired  combination  of 
gears  is  obtained  by  a  selector  lever  on  the  steering  wheel. 


CHAPTER   IX 
LUBRICATION   AND    COOLING   SYSTEMS 

Friction.  There  is  always  friction  between  any  two  sur- 
faces which  rub  or  "bear"  on  each  other.  Of  two  sets  of 
rubbing  surfaces  each  of  the  same  materials,  the  smoother 
set  will  obviously  have  the  less  friction.  But  even  what 
we  may  call  a  smooth  surface  will  appear,  when  looked  at 
through  a  microscope,  to  be  not  at  all  smooth  as  it  appears 
to  the  naked  eye.  Fig.  194  shows  the  relative  roughness 
as  seen  through  the  microscope  of  two  carefully  polished 
plates  of  brass  and  of  steel.  There  are  a  greater  number 


PIG.  194. — Surfaces  of  Brass  and      FIG.  195. — Surfaces   of  Brass  and 
Steel.  Steel  with  Lubrication. 

of  rough  places  in  the  steel  than  in  the  brass,  yet  some 
of  the  rough  places  will  fit  into  each  other,  and  the  surfaces, 
especially  if  pressed  together  as  they  would  be  when 
weighted,  will  offer  resistance  to  any  sliding  movement, 
tending  to  increase  the  roughness. 

Practically  all  the  resistance  to  sliding  can  be  removed, 
however,  if  such  moving  parts  are  separated  by  a  film  of 
engine  oil  as  illustrated  in  Fig.  195.  The  oil  acts  as  a  sort 
of  cushion  and  to  a  large  extent  prevents  the  fitting  together 
of  the  rough  places  in  the  two  surfaces.  This  figure  gives 
an  exaggerated  idea  of  the  fundamental  principle  of  all 
methods  of  lubrication;  and  lubrication  is  successful  only 
223 


224  GASOLINE  AUTOMOBILES 

so  long  as  a  film  of  lubricating  liquid  is  maintained  between 
the  polished  surfaces  bearing  on  each  other.  The  oil  film 
may  be  destroyed  either  (1)  because  no  more  oil  can  be 
supplied  to  the  bearing  surfaces;  or  (2)  because  the  bearing 
surfaces  are  loaded  too  heavily  and  are  pushed  together 
with  so  much  force  that  the  oil  film  is  broken  and  the 
conditions  shown  in  Fig.  194  results.  In  either  Case  the 
removal  of  the  oil  film  will  make  the  surfaces  wear  away 
rapidly. 

Surfaces  Requiring  Friction.  It  is  essential  that  the  fric- 
tion of  the  various  bearings  in  the  engine,  speed-change 
gears,  axles,  etc.,  be  made  small  so  as  to  waste  as  little 
as  possible  of  the  driving  power.  On  the  other  hand  there 
are  parts  of  an  automobile  such  as  the  brakes  which  should 
have  no  lubrication,  or  the  friction  clutch  which  in  most 
types  should  also  have  none.  The  brakes,  friction  clutch, 
and  the  tires  depend  for  their  efficient  action  on  large 
frictional  resistance  over  relatively  small  areas. 

Oil  in  the  Cylinders.  Primarily,  the  tightly  fitting 
cast-iron  rings  on  the  engine  pistons  are  to  prevent  the 
explosive  mixture  admitted  to  the  cylinders  above  the  pistons 
from  escaping  downward  past  the  pistons  into  the  crank 
case.  Inside  the  engine  crank  case  of  modern  type  engine 
oil  is  splashed  and  sprayed  continuously  so  that  on  the 
up-stroke  of  each  of  the  pistons  the  inside  of  the  cylinder 
is  wetted  completely  by  the  oil.  On  the  down-stroke  of 
the  piston,  practically  all  this  oil  should  be  swept  down 
by  the  piston  rings,  leaving  only  a  thin  film  on  the  cylinder 
walls  for  lubrication.  If  the  engine  oil  used  is  too  thin 
or  the  piston  rings  do  not  fit  tightly  enough,  too  much  oil 
will  accumulate  on  the  cylinder  walls  and  some  of  it  will 
get  into  the  explosion  space  at  the  top  of  the  cylinder. 
This  excessive  oil  will  be  only  partly  burned  as  it  is  not 
so  combustible  as  gasoline  and  will  make  a  black  deposit 
of  carbon  on  the  inside  of  the  cylinder,  on  the  spark  plugs, 
and  on  the  valves.  If  this  leakage  of  oil  is  in  sufficient 
amount  it  will  make  a  whitish  exhaust  smoke.  Whatever 


LUBRICATION  AND  COOLING  SYSTEMS  225 

system  is  used  for  lubrication,  one  must  be  cautious  to  avoid 
getting  too  much  oil  past  the  piston  rings  to  the  top  of  the 
engine  cylinder. 

If  there  is  continual  trouble  with  carbon  deposits  in 
engine  cylinders,  a  little  kerosene  poured  in  through  the 
priming  cocks  or  through  the  holes  for  the  spark  plugs  will 
loosen  the  carbon  so  that  it  will  be  discharged  with  the 
exhaust  gases.  Kerosene  will  not,  however,  prevent  the 
formation  of  carbon  and  the  treatment  must  be  repeated 
once  or  twice  a  week. 

When  the  engine  is  running  with  the  throttle  valve  of 
the  carbureter  nearly  closed,  there  will  be  only  a  small 
amount  of  explosive  mixture  entering  the  cylinders  and  in 
consequence  there  is  a  decided  vacuum  on  each  intake  stroke 
of  the  piston.  This  vacuum  has  a  tendency  to  draw  oil  past 
the  piston  into  the  combustion  chamber,  where  it  burns  and 
forms  smoke.  This  is  why,  when  an  automobile  is  left 
standing  with  the  engine  running  for  any  length  of  time, 
it  will  often  be  found  to  start  away  with  clouds  of  smoke 
issuing  from  the  exhaust. 

Kinds  of  Lubricants.  Commonly  used  lubricants  are 
either  liquids,  called  oils;  or  semi-solids,  called  greases  and 
semi-fluid  oils.  Oils  are  ordinarily  used  for  the  lubrication 
of  all  parts  of  the  engine  and  its  auxiliary  parts  included 
in  the  engine  casing.  Greases  and  semi-fluid  oils  are  used 
for  the  speed-change  gears,  differential  gears,  axles,  wheels, 
steering  gear  and  springs.  Some  of  the  latter  are  lubricated 
in  many  of  the  latest  designs  with  oil,  especially  for  such 
parts  like  springs  where  only  small  amounts  of  oil  or  grease 
are  needed.  One  reason  for  the  more  extended  use  of  oil 
instead  of  grease  is  that  grease  is  difficult  to  handle  and 
the  filling  of  grease  cups  or  containers  is  "messy"  work. 
Some  dealers  now  sell  grease  in  tablets  to  fit  the  standard 
sizes  of  grease  cups.  This  method  eliminates  much  of  the 
objection  to  the  use  of  grease  for  small  bearings. 

Only  mineral  oils  should  be  used  for  the  oil  supply  of 
gasoline  engine  cylinders.  A  vegetable  oil,  castor  oil,  is 


226  GASOLINE  AUTOMOBILES 

generally  used  for  the  engines  of  racing  automobiles  and  for 
aeroplane  engines  because  of  the  very  high  temperature  which 
it  will  withstand;  but  is  unsuitable  for  ordinary  automobile 
engines  which  operate  at  much  lower  cylinder  temperatures, 
because  it  tends  to  produce  an  excessive  amount  of  carbon 
in  the  cylinders  and  is  besides  expensive.  Steam  engine 
cylinder  oil  is  not  suitable,  first,  because  it  is  as  a  rule 
too  thick  (too  heavy  "body")  and  if  of  ordinary  power 
plant  grade  will  not  withstand  the  heat  in  the  cylinders  of 
gasoline  automobile  engines.  It  has  its  proper  place  for 
engine  lubrication  in  steam  automobiles. 

The  ideal  oil  for  gasoline  engine  cylinders  would  have 
either  of  the  two  following  qualities:  (1)  burning  up  com- 
pletely if  it  got  up  past  the  piston  rings,  so  that  there  would 
be  no  carbon  deposit,  or  (2)  not  burning  at  all  and  would 
remain  as  oil  no  matter  how  high  the  temperature  in  engine 
cylinders.  No  oil  can  be  made  to  meet  such  a  requirement. 
To  determine  quality,  oils  are  tested  (1)  for  flash  point;  that 
is,  the  temperature  at  which  a  film  of  it  will  break  down 
by  vaporization,  and  (2)  for  viscosity,  showing  at  what  tem- 
perature it  becomes  so  thin  as  to  be  worthless  as  a  lubricant. 
A  good  oil  should  have  enough  "body"  to  maintain  an  oil 
film  between  the  piston  and  the  cylinder  at  the  usual  tem- 
peratures in  automobile  engines  and  still  it  should  not  be 
so  thick  as  to  interfere  with  the  easy  movement  of  the  piston 
rings  in  the  cylinder. 

A  good  quality  of  engine  oil  should  be  free  from  acids, 
which  have  a  tendency  to  make  the  working  surfaces  of  both 
the  cylinder  and  pistons  rough. 

Flash-point  Test.  If  oil  is  heated  slowly  in  a  cup  in 
which  the  bulb  of  a  thermometer  is  immersed  and  the  flame 
of  a  taper  or  lighted  match  is  held  over  the  surface,  it  is 
not  difficult  to  observe  the  temperature  at  which  there  is 
sufficient  vapor  escaping  from  the  oil  to  be  ignited.  This 
temperature  at  which  the  oil  vapor  ignites  is  called  the  flash 
point  of  the  oil.  A  good  automobile  engine  oil  should  have 
a  flash  point  not  much  less  than  400  degrees  Fahrenheit. 


LUBRICATION  AND  COOLING  SYSTEMS  227 

Fire  Test.  If  the  procedure  as  outlined  above  for  the 
flash  test  is  continued  so  that  instead  of  having  momentary 
ignition  flashes  near  the  surface  of  the  oil,  the  whole  surface 
of  the  oil  takes  fire  and  continues  to  burn,  the  observed  tem- 
perature is  called  the  fire  test. 

Acid  Test.  A  simple  method  to  test  for  acid  in  oil  is 
to  dissolve  a  small  amount  of  the  oil  in  warm  alcohol  and 
dip  a  piece  of  blue  litmus  paper  in  the  solution.  If  there 
is  acid  in  the  oil  it  will  turn  the  paper  red.  Litmus  paper 
can  be  purchased  at  drug  stores. 

Oils  and  Greases  for  Automobiles.  Most  dealers  in  auto- 
mobile engine  oils  have  three  grades  according  to  thinness: 
(1)  light,  (2)  medium,  and  (3)  heavy.  Only  the  light  and 
medium  grades  should  be  used  in  engines  having  reasonably 
tight  or  close-fitting  piston  rings.  Heavy-grade  oil  may 
be  used  for  engines  with  piston  rings  which  are  not  as  tight 
as  they  should  be,  and  is  invariably  used  for  all  kinds  of 
air-cooled  automobile,  and  motor  cycle  engines.  Sometimes 
because  of  faulty  ignition  or  other  causes  an  engine  becomes 
so  much  heated  that  light  and  medium  oil  give  little  lubrica- 
tion and  are  used  up  too  rapidly.  The  only  remedy  then 
is  to  use  a  temporarily  heavier  grade. 

The  very  thick  oil  (semi-fluid)  of  the  kind  used  for  the 
lubrication  of  speed-change  gears  or  transmissions  as  well 
as  also  for  the  differential  gears  in  the  rear  axle  should 
be  of  a  kind  that  will  adhere  to  the  gear  teeth  for  cushion- 
ing effect,  thus  reducing  both  wear  and  noise.  The  speed- 
change  gears  should  be  well  provided  with  oil,  so  that  the 
lower  teeth  of  the  smallest  gears  will  be  in  oil  for  their 
full  length.  The  differential  gears  should  be  filled  with 
heavy  semi-fluid  oil  up  to  the  level  of  the  filling  hole,  making 
the  gear  casing  in  the  rear  axle  about  one-third  full.  The 
rear  axle  is  not  fluid-tight  so  that  if  relatively  thin  oil  is 
used  in  the  differential  casing  it  may  leak  from  the  ends 
of  the  axles  and  splash  over  the  brake  bands,  wheels,  and 
rear  axle.  This  leakage  oil  may  interfere  with  the  proper 
action  of  the  brakes  by  reducing  their  friction  and  its 


228  GASOLINE  AUTOMOBILES 

removal  is  difficult  without  spoiling  the  paint.  In  case  oil 
in  the  differential  works  out  at  the  ends  of  the  axles,  either 
a  heavier  grade  of  transmission  oil  should  be  used  or  closer 
fitting  washers  should  be  put  at  the  ends  of  the  axles.  Wheel 
bearings  are  packed  in  thin  cup  grease  which  need  not  be 
replaced  often  if  the  wheels  are  not  removed.  Heavy  grease 
will  not  cling  to  roller  or  ball  bearings  such  as  are  used 
in  the  wheels  of  automobiles. 

The  lubrication  of  the  steering  gear  is  important  as  its 
failure  may  cause  a  serious  accident.  Its  parts  should  be 
inspected  when  oiling  an  automobile  to  make  sure  there 
is  no  undue  wear.  Grease  and  oil  cups  on  the  steering  gear, 
including  the  rods  and  levers  connecting  it  to  the  front 
wheels  should  always  be  kept  well  filled  and  should  be  tested 
to  see  that  the  lubrication  gets  to  the  joints  for  which  it 
is  intended.  It  is  a  good  practice,  especially  where  grease 
is  used  to  screw  down  the  thread  on  the  grease  cups  till 
just  a  little  grease  can  be  seen  oozing  out  from  the  bearing. 

Insufficient  lubrication  in  the  engine  is  often  the  cause 
of  very  large  repair  bills,  and  in  the  steering  gear,  of  dis- 
astrous accidents.  It  pays  to  look  carefully  after  the  lubri- 
cation of  an  automobile.  Lubrication  is  cheaper  than  bearings. 

When  an  expert  looks  into  the  condition  of  an  automobile, 
one  of  the  first  places  he  inspects  for  wear  is  at  the  steering 
knuckles.  A  constant  supply  of  good  grease  or  oil  is  needed 
to  prevent  excessive  wear  at  the  knuckles.  It  is  worth  while 
to  screw  down  on  the  grease  cups  on  the  steering  knuckles 
every  time  oil  is  put  in  the  engine.  When  a  grease  cup 
is  screwed  down  so  that  it  cannot  be  turned  further,  it 
should  be  filled  immediately.  There  should  be  enough  grease 
in  the  cups  to  keep  forcing  it  out,  so  that  grit  cannot  get 
into  the  bearings. 

The  spring  shackle  bolts  are  sometimes  equipped  with 
grease  cups,  and  often  the  passages  for  the  grease  become 
clogged  so  that  one  may  screw  down  on  the  cup  and  only 
force  the  grease  out  of  the  thread  of  the  cup,  instead  of 
into  the  bearing,  as  the  grease-cup  cap  fits  loosely  upon  the 


LUBRICATION  AND  COOLING  SYSTEMS  229 

thread.  In  that  case  the  grease  cup  should  be  taken  off  and 
the  passages  cleaned. 

There  are  fewer  grease  cups  used  on  automobiles  now 
than  formerly.  Oil  cups  are  being  used  instead,  largely 
because  they  are  more  conveniently  filled. 

At  least  once  a  year  a  small  amount  of  grease  should 
be  put  between  the  leaves  of  automobile  springs  to  keep 
them  in  good  operating  condition  without  squeaking.  This 
can  be  done  by  raising  the  frame  with  an  automobile  jack 
which  has  been  blocked  up  high  enough  for  the  purpose. 
When  the  weight  on  the  frame  is  supported  by  the  jack 
it  is  not  difficult  to  insert  between  the  leaves  of  the  spring 
a  wedge-shaped  clamping  device  made  for  the  purpose,  or 
even  the  ends  of  a  screw-driver  will  do.  After  the  leaves 
have  been  separated,  the  very  small  amount  of  grease  needed 
can  be  easily  put  in. 

Oil  in  a  sense  wears  out  in  any  lubricating  system  and 
should  be  replaced  with  new  oil  occasionally.  Some  of  it 
will  work  up  past  the  piston  and  be  burned,  but  most  of  it 
will  remain  in  the  sump  longer  than  it  should  be  used.  All 
of  the  gasoline  that  is  taken  into  the  cylinder  is  not  burned. 
Some  of  k  is  forced  past  the  piston  on  the  compression 
stroke  into  the  crank  case,  where  it  condenses  and  mixes 
with  the  oil.  This  thins  the  oil  sometimes  to  a  point  where 
it  has  little  or  no  lubricating  value. 

Most  automobile  instruction  books  advise  draining  all 
the  oil  from  the  engine,  from  the  speed-change  gears,  and 
from  the  differential  case  at  the  end  of  every  1,000  or  2,000 
miles,  depending  somewhat  on  whether  the  driving  has  been 
heavy  or  light.  After  removing  the  old  oil  or  semi-fluid 
grease  from  these  parts,  they  should  be  flushed  with  kerosene 
in  order  to  remove  all  sediment  and  metallic  dust  that  may 
have  accumulated.  Heavy  continuous  service  requires  more 
attention  to  lubrication  than  light  service.  Both  before  and 
after  a  long  touring  trip  over  rough  roads  an  automobile 
should  be  given  careful  inspection  for  loose  parts,  excessive 
wear  in  important  parts,  and  lubrication. 


230  GASOLINE  AUTOMOBILES 

If  the  oil  supply  should  be  exhausted  while  the  auto- 
mobile is  in  use,  the  engine  will  get  stiff,  lose  its  power, 
and  the  friction  of  the  unlubrieated  parts  will  generate 
sufficient  heat  to  melt  out  the  lining  of  the  bearings.  If 
the  engine  runs  for  any  length  of  time  in  this  condition, 
it  may  be  wrecked  beyond  repair. 

An  automobile  owner  should  not  rely  entirely  on  his 
chauffeur  for  the  care  of  parts  of  the  automobile  requiring 
lubrication,  unless  he  has  found  out  that  the  man  knows 
the  importance  of  lubrication.  Nor  should  it  be  taken  for 
granted  that  the  garage  man  is  attending  to  the  lubrication 
of  an  automobile  when  he  charges  for  that  service.  "Make 
sure  yourself"  is  the  best  rule. 

Methods  of  Engine  Lubrication.  Lubricating  systems  for 
automobile  gasoline  engines  are  usually  of  one  of  the  three 
following:  (1)  simple  splasli  system,  which  is  entirely  auto- 
matic, no  pump  being  used;  (2)  splash  system  with  an  oil 
pump,  as  an  auxiliary;  (3)  fully  forced  feed  (pump] 
system. 

Simple  Splash  System.  In  many  medium  and  low-price 
models  of  automobile  engines,  engine  oil  is  poured  into  the 
crank  case  to  a  level  where  the  engine  crank  shaft  dips 
into  it  at  each  revolution.  The  rapid  rotation  of  the  cranks 
through  the  oil  in  the  bottom  of  the  crank  case  splashes 
it  in  all  directions  and  produces  a  sort  of  oil  foam  that 
covers  the  entire  inside  surface  of  the  crank  case  and  of 
the  cylinders  below  the  pistons  Each  bearing  has  a  hole 
drilled  at  a  place  where  the  "splashed"  oil  can  reach  and  then 
run  down  into  the  bearing. 

The  difficulty  with  this  system  is  that  if  the  oil  level 
is  a  little  too  high  there  will  be  over-lubrication,  that  is 
too  much  oil  will  be  splashed,  especially  into  the  cylinders, 
and  if  the  crank  shaft  does  not  dip  deeply  enough  there 
will  be  too  little  splashed  oil  to  lubricate  the  bearings 
properly.  Frequent  filling  is  therefore  necessary  to  maintain 
the  proper  oil  level.  This  system  is  shown  dia grammatically 
in  Fig.  196. 


LUBRICATION  AND  COOLING  SYSTEMS 


231 


A  modification  of  this  method  is  used  in  the  Ford  auto- 
mobile engine.  Besides  the  crank  shaft  the  flywheel  (which 
is  enclosed  in  the  engine  casing)  runs  with  the  lower  part 
of  its  rim  below  the  normal  oil  level,  and  by  its  rotation 
picks  up  and  then  throws  oil  in  all  directions.  Some  of 
this  splashed  oil  is  caught  in  a  nearby  horizontal  tube  having 
a  funnel  shaped  opening  along  side  of  the  flywheel  for 
collecting  the  oil  which  it  discharges  from  the  other  end  of 
the  pipe  upon  the  timing  gears.  As  the  friction  clutch  and 
planetary  gears  (transmission)  of  a  Ford  engine  are  intended 


FlG.  196.— Splash  Spstem  of  Lubrication. 

to  run  in  oil,  they  are  lubricated  also  by  the  splash  from  the 
flywheel. 

Some  device  such  as  a  float  indicator,  gage,  or  try-cock 
must  be  provided  so  that  the  level  of  oil  in  the  crank  case 
can  be  readily  determined.  Allowance  must  always  be  made 
for  the  possible  sticking  of  floats  and  for  the  automobile 
being  lower  on  one  side  than  the  other.  Observations  of 
oil  level  taken  when  the  engine  is  running  mean  nothing 
as  at  slow  speed  nearly  all  the  oil  may  be  in  the  crank  case 
while  at  high  speed  comparatively  little  may  be  there.  Ob- 
servations should  be  made  a  few  minutes  after  the  engine 
has  been  stopped. 

Splash  System  with  an  Oil  Pump.  As  an  improvement 
over  the  simple  splash  system  a  method  has  been  devised 
to  control  the  oil  level  by  mechanical  means.  A  typical 
device  of  this  kind  is  shown  in  Fig.  197,  which  is  in  use 
in  a  great  many  makes  of  automobiles.  As  shown,  there 
is  a  little  pan  or  cup  under  each  crank.  These  are  so 
arranged  as  to  height  that  when  filled  with  oil,  a  short 


232 


GASOLINE  AUTOMOBILES 


"spoon"  at  the  lower  end  of  the  connecting  rod  touches  the 
surface  of  the  oil  at  its  low  point  in  each  revolution  and 
splashes  oil  in  all  directions  over  the  inside  of  the  crank 
case,  and  over  practically  all  the  working  parts  of  the 
engine.  This  splashing  and  agitation  of  the  oil  makes  a 
fog  of  oil  in  the  crank  case  so  that  a  film  of  oil  is  deposited 
even  on  those  parts  which  the  splash  does  not  reach.  At  the 
right-hand  side  of  the  figure  an  engine-driven  pump  is  shown 
also  diagrammatically  which,  when  the  engine  is  running, 
pumps  oil  from  the  reservoir  or  "sump"  in  the  bottom  of 


FlG.  197. — Splash  and  Pump  System  of  Lubrication. 


the  crank  case  to  a  horizontal  distributing  pipe,  P.  There 
are  holes  in  the  side  of  this  pipe  from  which  oil  discharges 
into  the  pans  to  keep  them  constantly  over-flowing  and, 
therefore,  also  at  a  constant  level.  The  oil  is  constantly 
drained  back  into  the  reservoir  to  be  pumped  back  again 
into  the  pans.  This  system  maintains  constant  conditions 
of  lubrication  irrespective  of  the  amount  of  oil  in  the  reser- 
voir, consequently  this  reservoir  can  be  made  large  to  hold 
a  large  amount  of  oil  and  makes  frequent  refilling  unneces- 
sary. This  method  is  also  sometimes  called  the  constant-level 
splash,  but  although  left  out  of  this  name,  the  pump  is  an 
essential  part. 


LUBRICATION  AND  COOLING  SYSTEMS  233 

In  this  system  the  principal  cause  of  trouble  is  too  much 
oil  in  the  sump,  so  that  the  level  reaches  above  the  splash 
pans.  Sometimes  the  projections  on  the  connecting  rods  are 
so  large  that  too  much  oil  is  splashed  when  the  level  is 
normal. 

There  are  so  many  varieties  of  oil  pumps  that  no  descrip- 
tion will  be  given  here.  There  is  usually  sufficient  informa- 
tion regarding  the  oil  pump  in  the  automobile  instruction 
books  furnished  by  manufacturers.  A  small  oil  gage  or  pres- 
sure gage  is  shown  in  the  figure  in  a  branch  of  the  pipe 
leading  from  the  pump  to  the  oil  pipe  P.  There  is  no  flow 
of  oil  through  the  gage.  It  shows  merely  the  pressure  in 
the  oiling  system.  This  gage  is  intended  for  attachment 
to  the  dash  or  instrument  board  so  that  the  driver  can  see 
from  his  seat  whether  oil  is  being  properly  distributed.  One 
will  soon  observe  what  the  reading  should  be  for  ordinary 
operating  speeds.  When  the  needle  at  the  usual  speeds 
does  not  nearly  reach  this  gage  reading,  it  is  an  indication 
that  there  is  not  enough  oil  in  the  reservoir  to  run  the 
pump  full,  or  the  pipe  is  clogged.  This  is  a  warning  to 
get  more  oil  or  to  investigate  for  trouble  in  the  oil  piping. 
When  the  gage  .needle  hangs  at  zero  on  its  scale,  the  danger 
point  is  being  reached  as  regards  oil  supply.  If  the  oil  gage 
reading  increases  as  the  speed  of  the  engine  increases,  there 
is  a  good  indication  that  the  oil  is  circulating. 

Fully  Forced  (Pressure)  System  with  a  Pump.  In  a 
fully  forced  system  there  are  no  splash  devices  of  any  kind 
and  the  oil  for  lubrication  is  distributed  to  all  parts  of  the 
engine  and  its  auxiliaries  through  a  system  of  branch  pipes 
carrying  oil  under  pressure  from  the  oil  pump,  which  draws 
the  oil  from  a  reservoir  in  the  crank  case.  This  system  is 
shown  diagrammatically  in  Fig.  198.  Pipes  carry  oil  from 
the  pump  to  the  main  crank  shaft  bearings  B,  B,  B,  and 
there  are  holes  drilled  through  the  inside  of  the  crank  shaft 
(H,  H,  H,  H,)  so  that  the  oil  forced  into  the  main  bearings 
is  also  forced  through  the  shaft  and  out  into  the  connecting 
rod  bearings  on  the'  crank  shaft.  Since  the  oil  is  always 


234 


GASOLINE  AUTOMOBILES 


under  pressure  in  all  the  main  bearings  it  insures  positive 
lubrication  in  distinction  from  "hit  and  miss."  Bearings 
oiled  by  this  method  are  likely  to  last  a  very  long  time.  The 


Fie.  198. — Fully  Forced  (Pressure)  System  of  Lubrication. 

oil  escapes  from  the  forced  system  at  the  edges  of  the  con- 
necting rod  bearings  and  is  discharged  with  so  much  pres- 
sure that  it  is  distributed  as  a  fine  spray  penetrating  to 


Pressure  Oacje  -., 


Adjustable  Pressure 


Ya/ve- 


Connecting 
Rod  Bearings^ 


Camshaft  Bearings 


__  Reservoir 

Oil  Pump 

FIG.  199. — Lubrication  System  for  Eight-cylinder 
("Twin  Four")  Engine. 

every  part  including  the  pistons,  cylinders,  and  cam  shaft 
bearings. 

This  system  is  used  in  nearly  all  eight-  and  twelve-cylinder 
engines,  as  well  as  also  in  many  six-cylinder  engines.  A 
typical  example  is  shown  in  Fig.  199. 


LUBRICATION  AND  COOLING  SYSTEMS  235 

Lubrication  of  Knight  Slide  Valves.  One  method  of 
lubricating  the  sliding  sleeve  valves  of  Knight  engines  is  a 
modification  of  the  fully  forced  system  described,  except 
that  instead  of  all  the  oil  going  through  the  crank  shaft 
being  sprayed  from  the  ends  of  the  connecting  rods,  some 
of  it  passes  up  through  a  tube  inside  the  connecting  rod 
to  hollow  piston  pins  and  from  the  two  open  ends  of  their 
pins  it  flows  by  gravity  over  the  sleeves  and  is  distributed 
through  holes  and  oil  grooves  over  their  cylindrical  surfaces. 

ENGINE  COOLING  SYSTEMS 

Very  high  temperatures  result  at  the  tops  of  both  the 
cylinders  and  the  pistons  of  gasoline  engines  every  time 
there  is  an  explosion  stroke.  At  these  times  the  temperature 
rises  to  about  2800  degrees  Fahrenheit,  a  sufficiently  high 
temperature  to  make  the  iron  of  the  cylinder  red  hot,  and 
all  the  oil  provided  for  lubrication  would  be  burned  up, 
if  no  special  means  of  cooling  are  provided.  The  first  prin- 
ciple of  engine  cooling  is  to  get  the  most  economical  opera- 
tion, and  this  means  that  the  engine  should  be  kept  just 
cool  enough  to  prevent  the  cylinder  lubricating  oil  from 
burning  off  the  curved  surface  of  the  piston.  The  most 
commonly  used  method  of  reducing  the  temperature  of  gaso- 
line engine  cylinders  is  by  the  circulation  of  water  in  an 
enclosed  space,  called  the  water  jacket,  which  is  made  a  part 
of  the  outside  of  the  cylinder  casting,  and  surrounds  also 
the  valve  chambers.  By  keeping  a  supply  of  water  passing 
through  this  jacket  the  engine  cylinder  can  be  kept  cool 
enough  to  prevent  distortion  of  the  metal  surfaces  as  might 
result  from  overheating  and  to  prevent  also  the  burning  up 
of  oil  provided  for  lubrication. 

In  some  engines  the  water  is  self-circulating  through  the 
water  jackets  of  the  engine  cylinders,  but  in  others  the 
water  is  pumped  so  that  there  is  a  positive  circulation  at 
all  times  when  the  engine  is  runnirig. 

Air-cooled  engines  have  arrangements  to  provide  un- 
usually efficient  air  circulation  and  in  large  volume  over 


236  GASOLINE  AUTOMOBILES 

the  hottest  parts  of  the  engine  cylinders,  which  are  provided 
with  ribs  or  flanges  of  metal  on  the  outside  surface  of  the 
cylinder  which  are  in  most  cases  made  as  a  part  of  the 
cylinder  casting.  These  ribs  perform  a  service  similar  to 
that  of  the  water  jacket  on  other  engines.  The  method 
of  air  cooling  circulates  air  in  large  volume  for  cooling  the 
engine  cylinders  and  the  other  method  circulates  water.  The 
ribs  are  surrounded  by  a  circular  aluminum  sheet.  The  air 
spaces  between  the  ribs  and  this  sheet  are  the  only  openings 
between  the  top  and  bottom  compartments  separated  by  a 
plate.  There  are  fan  blades  on  the  flywheel  so  that  it  is 
used  for  a  suction  fan.  The  cool  air  enters  at  the  front  of 
the  engine  hood  into  the  top  compartment,  goes  down  be- 
tween the  ribs  on  the  engine  cylinders  and  passes  out  under 
the  frame  of  the  automobile.  The  amount  of  air  for  each 
cylinder  is  thus  mechanically  controlled  and  each  gets  about 
the  same  amount  and  with  most  efficient  contact  with  the 
cylinder  walls.  A  good  air-cooled  automobile  uses  no  more 
oil  than  one  that  is  water-cooled.  Air-cooled  engines  are 
usually  made  of  light  construction  so  that  they  are  not 
intended  for  large  engine  power. 

A  few  makes  of  automobiles  use  this  method  of  air  cool- 
ing, and  it  is  used  almost  exclusively  on  all  kinds  of  motor 
cycles.  The  method  of  air  cooling  is  so  simple  in  principle 
that  no  further  explanation  is  needed. 

Pump  System  of  Jacket  Water  Circulation.  Water  for 
cylinder  cooling  is  circulated  through  the  water  jackets  of 
an  automobile  engine  and  its  radiator  as  shown  in  Fig.  200 
by  means  of  a  small  pump  C.  The  direction  of  flow  of  the 
water  is  shown  by  arrows.  The  pipes,  made  usually  of  flexible 
rubber  hose,  are  connected  to  a  cooling  vessel,  R,  called  a 
radiator.  The  top  hose  is  connected  to  a  pipe  connection  at 
the  top  of  the  radiator,  and  the  lower  hose  to  the  bottom  of  the 
radiator.  Most  water  pumps  used  for  this  kind  of  service 
are  like  this  one  of  the  centrifugal  type,  and  are  operated 
by  gear  wheels  driven  by  the  engine  crank  shaft.  They 
are  similar  in  construction  to  an  ordinary  fan  blower 
for  air.  They  consist  simply  of  a  set  of  blades  or  vanes 


LUBRICATION  AND  COOLING  SYSTEMS 


237 


extending  out  from  a  central  shaft  like  the  spokes  of 
a  wheel.  A  pump  of  this  kind  depends,  as  its  name  indi- 
cates on  centrifugal  force  and  must  therefore  be  operated 
at  a  high  speed  to  be  effective.  Water  enters  the  pump 
around  the  shaft  and  is  driven  outward  by  the  centrifugal 
force  of  the  rapid  rotation  of  the  blades  and  discharges  from 


FIG.  200. — Pump  System. 

a  pipe  connected  to  the  outside  circumference  of  the  pump 
casing.  The  faster  the  engine  runs,  the  faster  the  water 
circulates. 

Another  type  of  circulating  water  pump  is  also  used.    It 
consists  simply  of  two  small  gear  wheels  which  are  placed  side 


Thermostatlc 
Valve 


FIG.  201. — Pump  System  with  Thermostatic  Valve. 


by  side  with  meshing  teeth.  These  gear  wheels  are  supported 
on  horizontal  bearings  in  a  casing  closely  fitting  the  teeth  all 
around,  except  at  the  places  at  the  top  and  bottom  of  the 
casing  where  the  teeth  are  in  mesh.  The  water  is  taken  into 
the  pump  at  the  bottom  of  the  casing  and  the  rotation  of  the 
gear  teeth  forces  it  from  a  discharge  opening  at  the  top  of 
the  casing. 

Fig.  201  shows  a  pump  system  of  cooling  water  circulation 


238  GASOLINE  AUTOMOBILES 

which  is  controlled  by  a  thermostatic  valve.  When  the  engine 
is  cold,  this  valve  is  open  and  by-passes  the  cooling  water  in 
the  engine  jackets  through  the  small  pipe  D  and  there  is  no 
circulation  through  the  radiator  R.  When  the  water  in  the 
jackets  becomes  heated  the  valve  closes  and  the  circulation  is 
through  the  radiator. 

A  device  of  this  kind  as  applied  to  a  Cadillac  engine  is 
shown  in  Fig.  202.  A  trap  for  collecting  overflow  of  water 
or  anti-freezing  solutions  which  are  sometimes  used  for  engine 


FIG.  202.— Cadillac  Thermostatic  Control. 

cooling  in  winter,  is  also  shown.  A  detail  of  the  pump  and 
thermostatic  valve  is  shown  in  Fig.  203.  A  similar  thermo- 
static system  of  cooling  water  control  is  used  in  Packard  and 
other  makes  of  automobiles. 

Thermo-syphon  Jacket  Water  Circulation.  The  method 
of  jacket  water  circulation  depends  on  the  principle  that 
cold  water  is  heavier  than  hot  water.  An  engine  cooled  by 
thermo-syphon  circulation  is  provided  with  two  water  con- 
nections or  pipes,  one  at  the  top  of  the  jackets  A  and  the 
other  at  the  bottom  B,  Fig.  204.  When  the  engine  cylinders 
become  heated,  the  hot  water  in  the  cylinder  jackets  tends  to 
rise  and  flow  upward  and  out  of  the  top  of  the  water  jackets 
into  the  top  of  the  radiator.  At  the  same  time  that  hot  water 


LUBRICATION  AND  COOLING  SYSTEMS 


239 


is  being  taken  out  of  the  water  jackets  at  the  top,  cool  water 
flows  in  through  the  bottom  hose  from  the  radiator,  and  this 
circulation  is  automatically  maintained  as  long  as  the  engine 


FIG.  203. — Cadillac  Water  Pump  and  Thermostatic  Valve. 

cylinders  are  hot  and  there  is  enough  water  in  the  radiator 
so  that  the  hot  water  hose  from  the  water  jackets  to  the 
radiator  contains  water.  This  means  that  the  radiator  must 


FIG.  204.— Thermo-Syphon  System. 


be  kept  practically  full  all  the  time.  If  the  hot  water  hose 
becomes  empty,  there  will  be  no  circulation,  the  water  in  the 
water  jackets  will  boil  away,  and  increasing  temperatures  in 
the  engine  cylinders  will  interfere  with  operation.  The  cir- 
culation of  water  in  the  engine  cylinder  jackets,  piping,  and 


240 


GASOLINE  AUTOMOBILES 


radiator  by  this  system  is  shown  in  Fig.  205.    Fig.  206  shows 
the  cooling  water  circulation  in  the  Ford  engine. 


Radiator 


Air 


Cool  Wafer 


FIG.  205. — Thermo-syphon  Cooling  System  Showing 
Water  Circulation. 


______  RadiaforCap 

-—-;.".  .....  Filter  Neck 

_____  Top  Tank 

•  --".-.~  Splash  Plate 
*          "Over  flow  Tube 
-----  -Radiator  Jnlef  Connection 


-~""~"^\~~"_~~"~~^  Cylinder  Outlet  Hose 
-7^-a—  •—  «•  .....  ,-?!     "  ...........  Hose  Clip 

^^•5  —  a-  '"'"  -"-      .......  r-Qflinekr  Head 


\  '\-Lowerffose  Cfip 
\- Radiator  Outlet 


.......  —Cylinder  Casting 

.  Blinder  In  le-f' 
Connection 


\  \Connecfion 
\DrainCock 
*  Lower  Tank 

FIG.  206. — Cooling  Water  Circulation  in  Ford  Engine. 

Radiators.  As  used  on  most  pleasure  automobiles,  a 
radiator  is  composed  of  an  irregular  front  and  back  surface, 
somewhat  resembling  a  honey  comb  in  many  designs.  Two 
of  this  type  made  of  a  large  number  of  square  tubes  about 


LUBRICATION  AND  COOLING  SYSTEMS  241 

four  inches  long  which  are  "flared"  or  spread  out  at  the 
ends  E,  E,  are  shown  in  Figs.  207  and  208.  When  a  number  of 
these  flared  tubes  are  held  together  closely  with  their  ends 


\  /        '--  Wafer 
Air  Passages 

FIG.  207. — Honeycomb  Kadiator. 

touching  and  are  dipped  into  a  bath  B  of  tinsmiths'  solder 
as  shown  in  Fig.  209,  a  bundle  of  tubes  will  be  made  with 
square  openings,  0,  0,  0.  Between  the  openings  there  will 


FIG.  208. — Honeycomb  Kadiator  with  Crimped  Tubes. 

be  very  narrow  spaces,  all  communicating  with  each  other. 
A  large  number  of  these  flaring  tubes  when  soldered  together 
in  this  way  make  a  typical  automobile  radiator.  As  radiators 
are  set  up  the  flared  openings  are  toward  the  front  of  the 
automobile  for  the  purpose  of  having  air  pass  through  their 
openings  to  cool  the  hot  water  entering  the  top  of  the  radiator 
from  the  water  jackets.  The  cooling  action  by  means  of  this 


242 


GASOLINE  AUTOMOBILES 


air  circulation  is  increased  by  a  chain  or  belt  driven  fan 
placed  behind  the  radiator  as  shown  in  Fig.  205  which  by  its 
suction  through  the  openings  of  the  radiator  increases  the 


FlQ.  209.— Simple  Method  of  Making 
Eadiator  Tubes. 

&• 'Air Space 


FIG.  210.— Zig-Zag  Radiator  Construction. 

amount  of  cooling  air  going  through.  The  narrow  communi- 
cating spaces,  8  (Fig.  209)  comprise  the  principal  storage  space 
for  water  in  the  radiator,  and  it  is  therefore  obvious  that 


LUBRICATION  AND  COOLING  SYSTEMS 


243 


in  proportion  to  the  amount  of  water,  an  enormous  cooling 
surface  is  obtained  by  this  kind  of  construction.  This  air 
circulation  induced  by  the  fan  is  not  necessary  when 
the  automobile  is  going  at  high  speed  but  is  very  much 


Cooling 
•Flanges 


Tubes  for  Wafer 

FIG.  211. — Vertical  Water  Tubes  and 
Horizontal  Air  Tubes. 

needed  when  the  engine  is  running  ("idling")  and  the  auto- 
mobile is  standing  still,  or  when  the  automobile  is  running 
slowly  through  traffic-congested  city  streets.  This  kind  of 
radiator  is  called  a  "honeycomb"  or  cellular  type.  Other 


FIG.  212. — Vertical  Eadiator  Tubes. 


methods  of  radiator  construction  are  shown  in  Figs.  210  and 
211.  Some  radiators  are,  however,  made  of  vertical  tubes  with 
small  rings  over  the  outside  surface  as  shown  in  Fig.  212. 

Liquid  Solutions  for  Jacket  Cooling  in  Winter.  In 
northern  climates  where  water  in  an  automobile  radiator 
is  likely  to  freeze  in  cold  winter  weather,  a  substitute  for 
water  must  be  used.  Such  substitutes  are  called  anti-freez- 


244  GASOLINE  AUTOMOBILES 

ing  solutions.  The  solutions  most  commonly  used  are  the 
following:  Denatured  alcohol,  kerosene,  glycerine,  and  cal- 
cium chloride. 

Denatured  Alcohol  is  in  most  respects  very  satisfactory 
for  mixing  with  water  to  make  a  mixture  or  solution  of 
low-freezing  properties.  The  following  table  gives  for 
various  percentages  by  volume  of  alcohol  mixed  with  water, 
the  corresponding  freezing  points  and  specific  gravities: 

FREEZING  POINTS  OF  COOLING  LIQUIDS  FOB  WINTER  USE 

Denatured  Grain  Alcohol  Mixed  with  Water 

Per  cent  by  volume  Specific  gravity  Freezing 

of  alcohol  of  solution  point 

10  0.99  24°  F. 

25  0.97  7°  F. 

50  0.93  -32°  F. 

70  0.90  -57°  F. 

Denatured  Grain  Alcohol  and  Glycerine  (equal  parts)  Mixed  with  Water 

Alcohol  and  Freezing 

glycerine                                    Water  point 

15  per  cent  of  mixture  85  per  cent  20°  F. 

25  per  cent  of  mixture  75  per  cent  8°  F. 

50  per  cent  of  mixture  50  per  cent  -33°  F. 

An  alcohol  and  water  solution  has  no  destructive  effect 
on  rubber  tubing  or  on  any  kind  of  metal.  The  only  dis- 
advantage is  that  it  evaporates  more  rapidly  than  water, 
so  that  in  refilling  a  radiator,  it  is  necessary  to  add  more 
alcohol  than  water  in  order  to  keep  the  solution  of  a  standard 
strength.  For  this  replacement  mixture  the  values  of  specific 
gravity  given  in  the  above  table  are  convenient. 

Kerosene  mixed  with  water  makes  a  very  cheap  anti- 
freezing  solution  and  it  does  not  vaporize  readily.  In  such 
a  solution  the  wastage  may  be  safely  assured  to  be  all  water 
unless  the  kerosene  is  allowed  to  leave  the  radiator  through 
the  overflow  pipe  or  through  a  leak.  Kerosene  has  the  great 
disadvantage  that  it  very  rapidly  deteriorates  rubber  hose 


LUBRICATION  AND  COOLING  SYSTEMS  245 

connections  and  if  it  is  used,  the  only  safe  way  is  to  use 
radiator  connections  of  some  other  material  than  rubber. 
A  flexible  brass  tubing  is  made  which  has  no  rubber  inser- 
tion packing  in  the  flexible  folds  which  can  be  used.  Kero- 
sene has  the  further  disadvantage  that  it  does  not  mix  well 
with  water. 

Glycerine  has  the  same  disadvantage  as  kerosene  as 
regards  deteriorating  effect  on  rubber  hose  connections.  It 
is,  however,  very  expensive,  and  sometimes  contains  acids 
which  are  likely  to  attack  the  brass  in  the  radiator.  Test 
is  explained  for  oils  on  page  227. 

A  mixture  of  twenty  per  cent  by  volume  of  glycerine, 
twenty  per  cent  of  denatured  alcohol,  and  sixty  per  cent  of 
water,  gives  more  satisfactory  results  than  glycerine  alone, 
as  the  alcohol  has  apparently  a  tendency  to  reduce  the 
deteriorating  effects  of  the  glycerine  on  rubber  and  on  the 
other  hand  the  presence  of  the  glycerine  reduces  the  vaporiza- 
tion loss  of  alcohol.  In  the  proportions  given,  this  solution 
will  be  safe  from  freezing  at  twenty  degrees  Fahrenheit 
below  zero. 

There  are  numerous  commercially  prepared  anti-freezing 
solutions  sold  at  high  prices.  Most  of  them  are  made  up  of 
the  liquids  mentioned  here,  although  calcium  chloride  is 
favorite  material  for  such  solutions.  If  used  at  all  in  radiator 
solutions  it  should  be  chemically  pure.  The  greatest  dis- 
advantage from  its  use  is  that  as  the  result  of  evaporation, 
a  whitish  crust  will  be  formed  in  the  water  jackets,  pipes, 
and  top  of  the  radiator  which  has  a  tendency  to  clog  up 
and  interfere  with  good  water  circulation.  This  crust  is, 
however,  soluble  and  can  be  dissolved  when  fresh  clean 
water  is  put  into  the  radiator  and  jackets  and  then  heated 
by  "idling"  the  engine  with  retarded  "spark."  Calcium 
chloride  solutions  should  be  te'sted  for  acidity  as  suggested 
for  glycerine.  Commercial  calcium  chloride  (not  chemically 
pure)  is  almost  certain  to  set  up  electrolytic  action  when 
two  kinds  of  metals  are  joined  together,  as  for  example, 
in  the  parts  of  a  centrifugal  pump  or  at  a  brass  drain 


246  GASOLINE  AUTOMOBILES 

cock.  The  following  table  gives  the  freezing  temperatures 
for  several  mixtures  (by  volume)  of  saturated  solutions 
of  calcium  chloride  and  water. 

FREEZING  POINTS  OF  CALCIUM  CHLORIDE  SOLUTIONS  MIXED  WITH  WATER 

Per  cent  by 

volume  of  Specific  gravity  Freezing 

calcium  chloride  of  solution  point 

10  1.085  22°  F. 

20  1.119  0°  F. 

25  1.219  -18°  F. 

28  1.268  -42°  F. 


CHAPTER  X 
AUTOMOBILE  TROUBLES  AND  NOISES 

Modern  automobiles  have  been  perfected  to  such  a  degree 
by  high  engineering  skill  in  both  mechanical  and  electrical 
work  that  the  troubles  and  noises  now  occurring  are  indeed 
few  in  number  compared  with  the  automobiles  made  several 
years  ago.  In  this  connection  it  is  worth  while  noting  that 
dealers  in  second-hand  cars,  who  decide  their  buying  points 
for  an  automobile  by  the  amount  of  noise  it  makes  when 
running  make  their  prices  on  more  than  a  little  basis  of 
fact.  The  noise  an  automobile  makes  is  a  fairly  good  index 
to  its  condition  as  to  wear,  repair,  care  in  operation,  lubrica- 
tion, etc.  Many  automobiles  that  are  four  or  five  years 
old  but  have  been  carefully  used  and  kept  in  good  repair 
are  as  free  from  noises  as  some  cars  that  have  been  operated 
only  a  few  months,  and  their  serviceableness  for  future  use 
is  correspondingly  large. 

Carbon  Deposit  in  the  Cylinders  is  probably  the  most 
common  cause  of  trouble  in  automobile  operation.  It  is 
always  the  result  of  the  imperfect  combustion  (1)  of  engine 
oil  which  gets  to  the  top  of  the  cylinders,  past  the  piston 
rings  or  (2)  of  gasoline  which  has  not  mixed  in  the  right 
proportions  with  the  air  supply  or  (3)  the  mixture  of  gaso- 
line vapor  and  air  has  not  been  completely  ignited  on  every 
power  stroke  because  of  imperfect  spark  plugs  or  other 
defects  in  the  ignition  apparatus.  The  remedy  is  to  clean 
out  the  carbon.  The  easiest  way  to  get  an  idea  as  to  the 
condition  of  an  engine  cylinder  as  to  carbon  deposits  is  to 
take  out  a  spark  plug.  If  there  is  enough  carbon  deposit 
in  one  or  more  of  the  cylinders,  there  will  be  a  peculiar 
"pounding"  of  the  pistons  due  to  particles  of  red  hot  carbon 
igniting  the  explosive  mixture  before  the  spark  is  made. 
247 


248  GASOLINE  AUTOMOBILES 

The  "pounding"  therefore  is  the  same  kind  of  noise  heard 
when  the  spark  is  advanced  too  far  or  with  a  heavy  load 
going  up  a  grade,  the  spark  is  not  retarded.  If  the  plug 
has  been  in  that  particular  cylinder  for  some  time  and  has 
a  considerable  coating  of  carbon  on  the  porcelain  or  mica 
center  piece,  it  is  to  be  assumed  that  the  walls  and  exhaust 
valve  are  also  coated  and  need  cleansing.  The  best  way 
to  remove  carbon  deposits  is  to  have  it  burned  out  at  a 
repair  shop  with  oxygen-acetylene  flame  apparatus.  Another 
method  is  by  scraping  off  the  carbon  deposits  by  the  use 
of  tools  of  slightly  different  shapes  which  are  bent  so  that  they 
will  reach  into  and  scrape  over  the  end  of  the  piston  and 
the  walls  of  the  cylinder.  The  usual  method  is  to  scrape 
all  the  loose  carbon  to  the  exhaust  valve  and  when  the  work 
of  scraping  is  finished,  turn  the  engine  by  hand  till  the 
exhaust  valve  is  opened  wide  when  the  carbon  refuse  can 
be  pushed  into  the  exhaust  pipe,  and  when  the  engine  is 
started  it  will  be  discharged  with  the  engine  exhaust.  It 
is  recommended  that  after  finishing  with  the  scraping  tools, 
that  a  small  brush  be  used  to  remove  all  loose  particles  and 
that  finally  a  little  kerosene  be  poured  into  the  cylinders 
to  serve  as  a  "wash."  When  through,  examine  the  exhaust 
valve  and  its  seat  carefully  to  be  certain  no  particles  of 
carbon  remain  attached  which  would  interfere  with  proper 
closing.  It  is  a  good  idea  to  make  a  paste  of  flake  graphite, 
finely  powdered,  and  "cup"  grease  for  use  on  the  threads 
of  the  cylinder  plugs  over  the  valves.  When  replacing  the 
plugs,  be  sure  the  copper  gaskets  or  "washers"  are  put 
in  under  the  plugs,  as  putting  these,  together  with  using 
the  graphite  paste  on  the  threads  is  good  insurance  for  tight 
joints.  The  same  precautions  as  to  tightness  of  joints  should 
be  observed  whenever  replacing  spark  plugs.  Whenever 
greasy  spots  are  observed  around  valve  plugs,  it  is  an  indica- 
tion of  loose  joints,  which  are  always  wasteful  of  power  and 
prevent  getting  the  natural  pressure  on  the  compression 
stroke  necessary  for  best  efficiency.  The  use  of  copper  gas- 
kets and  graphite  paste  is  the  best  remedy. 


AUTOMOBILE  TROUBLES  AND  NOISES  249 

When  examining  spark  plugs  to  test  for  the  presence  of 
carbon  deposits,  it  may  be  observed  that  in  some  cases  the 
deposit  is  very  black  sticky  substance  which  adheres  firmly 
to  knives  and  tools.  This  kind  of  deposit  is  an  indication 
always  of  an  excessive  amount  of  engine  oil  getting  past 
the  piston  rings  and  finding  its  way  into  the  cylinder.  It 
may  be  that  most  of  the  carbon  in  such  case  is  deposited 
because  of  improper  mixtures  from  the  carbureter  of  gaso- 
line and  air,  but  in  any  event  the  excess  of  oil  is  the  cause 
of  part  of  the  deposit.  On  the  other  hand,  if  the  carbon 
deposit  is  dry  and  brittle  it  is  likely  to  be  due  almost  entirely 
to  improper  mixtures  of  gasoline  and  air,  to  the  same  cause 
as  that  producing  thick  black  smoke  in  the  discharge  from 
the  engine  exhaust  pipe. 

Kerosene  put  into  the  engine  cylinders  in  small  quan- 
tities, about  two  or  three  tablespoonfuls  at  a  time,  will,  in 
most  cases,  remove  small  carbon  deposits,  and  if  used 
regularly,  say  once  a  week,  may  prevent  further  trouble 
from  this  cause.  It  can  be  put  into  the  cylinders  most  easily 
by  fitting  the  little  cups  on  the  priming  cocks  or  by  squirting 
into  the  main  air  valve  of  the  carbureter  from  small  (com- 
pression bottom)  oil  can,  just  before  the  engine  is  stopped. 
When  kerosene  is  put  into  the  cylinders  by  either  method, 
the  engine  should  not  be  run  again  for  several  hours,  and 
when  it  is  started  there  should  be  thick  black  clouds  of 
smoke  coming  from  the  exhaust,  indicating  that  carbon  has 
been  removed.  Another  method  sometimes  used  is  to  run 
the  engine  for  about  fifteen  minutes  once  a  week,  with 
the  spark  well  retarded  as  for  starting,  and  inject  kerosene  at 
the  air  inlet  of  the  carbureter,  with  the  float  valve  of  the 
carbureter  held  down  and  closed. 

Grinding  the  Valves.  It  is  a  good  plan  to  grind  the 
exhaust*  valves  of  the  engine  at  the  same  time  that  the  valve 


*  The  intake  valves  make  less  trouble  than  the  exhaust  valves  because 
through  them  passes  cool,  fresh,  unburned  mixtures,  while  through  the 
exhaust  valves  pass  hot  soot,  burned  or  partly  burned  gases. 


250  GASOLINE  AUTOMOBILES 

plugs  are  removed  for  the  removing  of  carbon  either  by 
burning  or  by  scraping.  When  the  pressure  on  the  com- 
pression stroke  is  less  than  it  should  be,  it  is  most  often 
the  result  of  leaky  exhaust  valves,  which  do  not  close  tightly 
on  the  compression  stroke,  because  of  the  lodgment  of 
particles  of  carbon  and  therefore  permit  leakage  through 
them. 

Valve  grinding  begins  with  the  removal  of  the  valve 
plugs  on  the  cylinders  requiring  valve  grinding.  Next  the 
spring  (see  Fig.  173)  on  the  valves  must  be  removed  so 
that  the  valves  can  be  turned.  Then  lift  the  valves  for 
grinding  and  put  a  thin  coating  of  grinding  paste  on  the 
bevel  (conical)  part  of  the  valve.  A  satisfactory  paste  can 
be  made  of  powdered  emery  mixed  with  enough  kerosene 
to  make  a  thick  paste  and  then  add  a  few  drops  of  oil  in 
the  proportion  of  about  one  drop  to  each  tablespoonful  of 
kerosene  used.  Exact  proportions  are,  of  course,  not  essen- 
tial. It  is  best  to  make  two  kinds  of  this  paste,  one  with 
rather  coarse  emery  for  rough  cutting  and  another  with 
very  fine  emery  to  give  a  smooth,  clean  surface  for  finishing. 
Valve  grinding  pastes,  mixed  for  use,  can  be  purchased  at 
most  automobile  supply  stores. 

After  these  preliminary  operations,  a  special  valve  grind- 
ing tool,  a  carpenter's  brace  with  attached  screw-driver  or 
a  plain  hand  screw-driver  may  be  used  for  the  grinding. 
The  tool  or  screw-driver  fits  into  a  notch  like  the  head  of 
a  screw  in  the  top  of  the  valve.  The  grinding  is  done  by 
rotating  (oscillating)  the  valve  back  and  forth  until  the 
entire  bearing  surfaces  of  both  the  valve  and  its  seat  are 
made  clean  and  smooth.  The  valve  should  not  be  turned 
all  the  way  round,  as  one  would  bore  a  hole  with  a  brace, 
but  should  be  rotated  only  about  a  quarter  turn  with  light 
pressure.  Now  and  then  the  valve  should  be  lifted,  turned 
half  way  round  while  the  grinding  is  continued.  This  turn- 
ing is  for  the  purpose  of  getting  good  seating  of  the  valve 
in  all  positions,  as  without  the  turning  it  might  fit  well 
in  only  one  position.  Powdered  glass  is  sometimes  used. 


AUTOMOBILE  TROUBLES  AND  NOISES  251 

After  the  valve  grinding  is  finished,  the  valve,  its  seat, 
and  its  guide-rod  should  be  well  washed  in  gasoline, 
so  that  none  of  the  emery  paste  remains  to  scratch  the 
surface  of  the  valve  as  it  operates.  To  test  the  work  to 
see  that  it  is  well  done,  put  a  narrow  lead  pencil  line  all 
the  way  round  the  bevel  edge  of  the  valve  and  turn  the 
valve  all  the  way  around  several  times.  If  the  line  is  rubbed 
out  over  the  whole  circumference  the  valve  is  likely  to  be 
satisfactorily  tight. 

"Knocking"  or  "pounding"  in  the  engine  cylinders  may, 
in  addition  to  the  causes  already  mentioned,  such  as  red-hot 
particles  of  carbon  deposit,  or  an  excessively  hot  engine 
igniting  the  explosive  mixture  before  the  spark  is  made,  spark 
being  too  far  advanced  for  the  speed  and  kind  of  load,  also 
be  caused  by  loose  connecting-rod  bearings,  loose  piston 
wrist-pins,  and  loose  crank  shaft  bearings,  all  of  which 
are  in  most  cases  due  to  overheated  bearing  surfaces  caused 
by  insufficient  lubrication.  Infrequently,  however,  it  is  also 
caused  by  the  engine  getting  too  hot  on  a  warm  day,  when 
heavily  loaded,  or  because  of  a  loose  piston  or  broken  piston 
ring.  Trouble  with  bearings  such  as  are  listed  here  are  best 
remedied  by  a  skilled  mechanic.  Amateurs  who  are  not 
well  experienced  are  likely  to  make  bearings  much  too 
tight  after  having  them  apart  for  repairs  and  there  is  unend- 
ing trouble  until  the  bearings  get  either  "worn  in"  or 
"burned  out." 

A  rhythmic  "knocking"  is  also  caused  by  "missing" 
cylinders,  meaning  that  the  engine  cylinder  or  cylinders 
making  the  noise  are  not  firing  the  explosive  mixture  they 
are  receiving.  This  is  a  different  sound  from  the  knocking, 
due  to  loose  bearings  or  to  too  early  ignition,  and  further, 
if  only  one  cylinder  is  missing  the  sound  will  be  heard  only 
once  in  a  revolution.  It  is  less  observable  in  engines  of 
eight  or  twelve  cylinders  than  in  those  or  four  or  six 
cylinders.  It  is  usually  due  to  a  sooted,  defective,  or  broken 
spark  plug,  although  may  be  caused  by  a  broken  electric 
wire  from  the  distributer  to  the  spark  plug. 


252  GASOLINE  AUTOMOBILES 

"Tapping"  valve  rods  are  another  source  of  trouble.  The 
"tapping"  of  valve  rods  does  not  indicate  that  there  is  any- 
thing seriously  wrong  with  the  engine.  It  will  continue 
to  give  approximately  its  full  power  at  about  the  usual 
gasoline  consumption.  It  is  merely  an  annoying  noise  com- 
parable with  squeaking  of  springs  or  the  rattle  of  doors. 
The  "tapping"  noise  is  caused  by  gradual  wearing  away  of 
the  bevel  faces  of  valves  or  of  their  seats.  When  the 
valve  stems  are  properly  adjusted  with  respect  to  the  push 
rod  on  the  side  shafts  carrying  the  cams  for  opening  the 
valves,  there  is  a  little  space,  clearance,  between  the  bottom 
of  the  valve  stem  in  the  closed  position  and  the  top  of  the 
adjusting  screw  on  the  push  rod.  When  properly  adjusted, 
the  space  between  the  bottom  of  the  valve  stem  and  the 
top  of  the  adjusting  screw  is  not  much  more  than  the 
thickness  of  a  sheet  of  good  letter  paper.  It  should 
be  noted  that  there  is  much  more  likelihood  of  getting  poor 
engine  results  if  the  clearance  is  made  too  large  when  adjust- 
ing than  there  is  likely  to  be  from  any  wear  in  the  direction 
producing  valve  tapping.  Adjust  carefully  therefore  to  see 
that  the  clearance  is  not  made  too  large,  because  if  it  is 
too  large,  the  push  rod  does  not  lift  the  valve  the  full 
amount,  cutting  down  both  the  height  the  valve  is  lifted 
and  also  the  time  it  is  open.  Of  course  one  could  imagine 
the  condition  where  the  valve  stem  and  the  top  of  the  push 
rod  would  wedge  each  other  so  closely  (no  clearance)  that 
the  valve  could  not  in  any  position  get  down  on  its  seat. 
This  would  be  especially  bad  in  the  compression  stroke, 
when  the  explosive  mixture  in  the  cylinder  must  be  put 
under  pressure  by  the  upward  stroke  of  the  piston.  If 
either  the  exhaust  valve  or  the  inlet  valve  does  not  close 
properly,  the  necessary  pressure  for  efficient  combustion 
cannot  be  obtained. 

Some  authorities  claim  that  a  weak  spring  on  the  exhaust 
valve  can  be  a  cause  of  poor  engine  economy.  The  effect 
produced  is  that  the  exhaust  valve  because  of  the  light 
spring  will  open  automatically  on  the  suction  stroke  intended 


AUTOMOBILE  TROUBLES  AND  NOISES  253 

for  sucking  in  the  explosive  mixture  from  the  carbureter, 
and  that  some  of  the  burned  gases  from  the  previous  power 
stroke  will  be  sucked  into  the  cylinder  from  the  exhaust 
pipe.  Recent  experiments,  however,  show  that  the  efficiency 
of  combustion  is  actually  improved  by  the  mixing  of  a  small 
amount  of  the  burned  gases  with  the  fresh  charge. 

Valve  Timing  and  Setting  are  properly  the  work  for  only 
good  experienced  mechanics.  Instruction  books  prepared 
for  and  going  with  the  different  kinds  of  automobiles,  ex- 
plain the  method  for  each  kind  of  engine  in  detail,  with 
the  help  of  marks  of  various  kinds  on  the  flywheel,  on 
pointers,  and  on  timing  gears.  The  principles  have  been 
explained  in  the  various  preceding  chapters. 

Wrong  Explosive  Mixtures  are  the  result  of  incorrect 
proportions  of  gasoline  vapor  and  air  in  mixture  sucked  into 
the  engine  cylinders  from  the  carbureter. 

Flooded  Cylinder.  The  most  troublesome  condition  is 
when  the  mixture  in  the  cylinder  is  much  too  rich  in  gaso- 
line, so  that  it  will  not  explode.  Most  often  this  is  caused 
when  the  engine  is  turned  over  a  number  of  times,  either 
by  hand  or  with  a  starter,  and  because  of  temporarily  defec- 
tive ignition  there  are  no  explosions.  As  a  result,  there 
is  an  accumulation  of  drops  of  gasoline,  on  the  inside  of  the 
cold  cylinders,  which  have  separated  from  the  mixture,  most 
of  which,  of  course,  goes  out  through  the  exhaust  pipe.  This 
accumulation  of  drops  of  gasoline  is  rapid,  because  for  start- 
ing, especially  in  cold  weather,  mixtures  very  rich  in  gaso- 
line are  used.  In  this  way  it  is  easy  to  get  a  mixture  so 
largely  gasoline  that  it  cannot  explode  even  when  the  tem- 
porary difficulty  with  the  ignition  is  corrected.  The  simplest 
remedy  is  to  open  the  priming  cocks  on  all  the  cylinders 
and  continue  to  turn  the  engine  over  a  number  of  times,  so 
that  on  the  compression  strokes  the  mixture,  excessively 
saturated  with  gasoline  will  be  driven  out  through  the  open- 
ings in  the  cocks.  If  this  condition  in  the  cylinder  is  very 
bad,  the  gasoline  vapor  may  be  seen  at  the  discharge  open- 
ings of  the  cock.  If,  after  this  cleaning,  the  priming  cocks 


254  GASOLINE  AUTOMOBILES 

are  again  closed,  the  engine  will  usually  start  after  a  few 
turns  of  cranking. 

Flooded  Carbureter.  Somewhat  similar  results  to  those 
explained  above  result  from  getting  the  carbureter  thor- 
oughly wetted  inside  with  liquid  gasoline.  Some  people 
are  in  the  habit  of  always  manipulating  the  float  valve  on 
the  carbureter  by  hand  to  make  starting  easier.  This  is 
called  "priming  the  carbureter"  with  the  object  of  getting 
an  excessively  rich  mixture.  Not  infrequently  this  car- 
bureter manipulating  is  done  a  few  times  too  often  when 
there  is  some  temporary  trouble  with  ignition,  so  that  by 
the  time  ignition  trouble  has  been  corrected  the  mixture 
going  into  the  cylinders  from  the  carbureter  has  too  much 
gasoline  to  be  exploded.  There  are  two  simple  remedies: 
(1)  by  cranking  with  priming  cocks  open  as  for  flooded 
cylinder;  or  (2)  by  not  doing  any  more  cranking  for  about 
ten  or  fifteen  minutes,  after  which  time  the  excess  of  gaso- 
line in  the  carbureter  passages  will  probably  be  evaporated, 
so  that  cranking  will  then  start  the  engine  without  difficulty. 
Test  for  condition  of  carbureter  flooding  by  putting  a  finger 
into  the  air  inlet  tube. 

Sometimes  it  happens  that  a  bit  of  rubber  or  of  wood 
gets  under  the  float  valve  of  the  carbureter.  At  one  time 
this  was  a  common  carbureter  trouble  but  does  not  occur 
so  frequently  now  since  so  much  gasoline  is  purchased  from 
reliable  dealers  who  know  enough  to  avoid  the  use  of  hose 
connections  on  gasoline  filling  machines  which  contain  rub- 
ber or  rubber  compounds.  A  particle  of  rubber  or  other 
foreign  material  when  stuck  in  the  float  valve  may  cause 
continued  cylinder  and  carbureter  flooding.  The  obvious 
remedy  is  to  remove  the  cause.  Sometimes  it  can  be  removed 
by  shaking  the  float  valve,  but  usually  it  is  necessary  to 
take  the  carbureter  apart.  Now,  a  word  of  caution !  Unless 
circumstances  are  unusually  urgent,  do  not  spoil  the  adjust- 
ments of  a  good  carbureter  by  taking  it  apart  unless  besides 
knowing  all  about  the  theory  of  the  carbureter,  you  have 
had  practical  experience  in  the  adjustments  of  the  kind  of 


AUTOMOBILE  TROUBLES  AND  NOISES  255 

carbureter  used.  The  level  at  which  the  float  must  be  set 
is  always  determined  by  experiment  and  inexperienced  per- 
sons will  usually  do  a  great  deal  of  experimenting  before 
they  get  even  reasonably  satisfactory  adjustments. 

Carbureter  flooding  results  also  sometimes  from  the  float 
losing  its  buoyancy  by  filling  with  gasoline.  If  a  cork  float 
is  used  in  the  carbureter,  partial  loss  of  buoyancy  is  not 
unusual.  The  effect  is  to  make  the  float  heavier  than  it  was 
when  originally  adjusted  with  respect  to  the  float  valve 
and  will  permit  the  gasoline  to  stand  higher  in  the  gasoline 
or  float  chamber  than  was  intended.  High  gasoline  level  may 
make  gasoline  stand  in  the  orifice  tube  so  high  that  it  might 
be  overflowing  continually,  whether  or  not  the  engine  is 
running.  The  remedy  is  to  take  out  the  cork  float  and  after 
drying,  paint  it  with  shellac.  Baking  in  a  shellac  baking 
oven  is  desirable  if  equipment  of  this  kind  is  available. 

If  the  float  is  of  the  hollow  metal  kind,  the  loss  of 
buoyancy  is  due  to  holes  in  its  surfaces.  The  remedy  is  to 
empty  and  dry  the  float  and  then  close  the  hole  or  holes 
with  solder.  Floats  should  always  be  carefully  tested  for 
buoyancy  for  several  hours  before  they  are  put  into  place 
in  the  carbureter. 

Color  of  Flame  from  Priming  Cocks.  In  this  connection, 
it  is  interesting  to  observe  that  the  color  of  the  flame  from 
open  priming  cocks  is  a  good  indication  of  the  correctness 
of  the  proportions  of  the  explosive  mixture  in  the  engine 
cylinders.  If  the  mixture  is  of  satisfactory  proportions  to 
give  most  effective  explosions,  the  flame  has  a  bluish  color. 
When  the  flame  is  tinged  strongly  with  red,  the  mixture  is 
too  rich  in  gasoline ;  and  when  it  has  a  whitish  color  it  is 
much  too  weak  in  gasoline. 

Back-firing  into  the  Carbureter.  Most  modern  automobile 
engines  are  designed  so  carefully  that  there  is  little  trouble 
with  back-firing  into  the  carbureter  (see  page  101)  except 
when  the  mixture  going  into  the  cylinders  is  too  weak.  Weak 
mixtures  may  be  due  (1)  to  incorrect  adjustments  of  the 
carbureter  or  (2)  gasoline  supply  being  nearly  exhausted 


256  GASOLINE  AUTOMOBILES 

so  that  there  is  not  enough  to  maintain  the  proper  level  in 
the  carbureter  for  a  sufficiently  strong  mixture. 

A  weak  mixture  from  the  carbureter  at  low  engine  speeds 
is  usually  due  to  too  little  gasoline  in  the  mixture  (float 
valve  set  too  low)  ;  and  when  the  mixture  is  too  weak  only 
at  high  speeds  it  is  due  to  too  much  air  through  the  auxiliary 
air  valve  (auxiliary  air  spring  too  weak). 


INDEX 


Advance  of  spark,  125,  129,  165 
Air  cooling,  235 
Alcohol  for  fuel,  50,  51 

—  in  radiator,  244 
Alternating  current,  112,  168 

rectifier,  112,  113 

Ampere,   105 

Aniline,  53 
Armature,   149 
Atwater-Kent  ignition,  144 
Automatic  gear  shifts,  221 
Automatic  spark  advance,  125,  142 

,  Delco,  125 

,  North  East,  142 

Automobiles,  electric,  3 

— ,  gasoline,  4 

— ,  steam,  2 

— ,  types  of,  2,  4 

Axle  drive  shaft,  9,  208,  211 

Axles,  front,  13,  14,  203 

— ,live,   211 

— ,  rear,  9,  11,  206,  211 

Back-firing,  255 

Batteries,   dry,   105 

— ,  storage,  106 

Battery  charging,  107,  177 

—  connections,  115 

—  ignition,  12x 

—  troubles,  110 
Baume  hydrometer,  54 
Bendix  drive,  170 
Benzine,  49 


Benzol,  51 

Bevel  gear  drive,  207,  210 
Block  cylinders,  44 
Bodies,  types  of,  4,  5,  8 
Bore,   cylinder,   45 
Bosch  magneto,  156 

battery  ignition  system,  147 

Brakes,  10,  218 

— ,  adjustment  of,  219 

— ,  equalizers,    218 

— ,  failures,  220 

Braking   with   engine,  219 

Burton  process,  49 

Cabriolet,  5 

Cadillac  cooling  system,  238 

Calcium  chloride,  246 

Camber  of  front  wheels,  205 

Cam  shafts,  26 

Carbon   deposits,   103,   247 

Carbureter    adjustments,    101,    103 

— ,  auxiliary  air  valve,  67 

—  troubles,  100-103 

—  priming,  69 
Carbureters,  63-103 
— ,  Cadillac,  93-94 
— ,  Holley,   80-81 
— ,  Johnson,  89-90 
— ,  Kingston,  73-75 
— ,  Marvel,  75-76 

— ,  Packard,  94,  98-100 
— ,  Puddle  type,  74 
— ,  Kayfield,  85-86 


257 


258 


INDEX 


Carbureters,  regulated  nozzle,  70 

— ,  Schebler,  82-83,  91-92 

— •,  Stewart,  79-80 

— ,  Stromberg,  77-78 

— ,  Tillotson,  89 

— ,  Zenith,  87-88 

Cars,  (See  Automobiles) 

Cells,  (See  Batteries) 

Chain  drives,  170 

Change  gears,  9,   12,   188 

Charging  batteries,  107,  177 

Chassis,  8 

Clearance,  48 

Clutches,  9,  11,  28,  184 

Coils,  vibrating,  127,  131 

— ,  non-vibrating,   136,  138 

Color  of  exhaust,  102,  255 

Compression,  25,  50 

Condensers,  130,  136,  142 

Cone  clutches,  185 

Connecticut    ignition    system,    124, 

143 

Connecting  rod,   23 
Cooling  systems,  235 

—  solutions,  243 
Coupe,  4-6 

Cracking  gasoline,  49 
Crank  case,  23 

Crank  shafts,  9,  34,  46,  47 

Cycles,  23 

— ,  four,  23-28 

— ,two,   23 

Cylinder  arrangements,  28,  36 

—  cooling,  235 

—  oils,  226,  227 
Cylinders,  engine,  9,  28,  44 

Dash  control,  83 
Delco  ignition,  126,  140 

—  starter,  170,  173 
Detachable  cylinder  head,  45 
Differential  gear,  10,  207 
Dimming  resistance,  138,  182 
Direct  current,  112 


Direction  of  current,  114,  115 
Disk  clutch,   186 
Displacement,  piston,  48 
Distributor,    122,    163 
Distributing  arm,  122 
Doped   gasoline,   51 
Double  ignition,   158 
Drag  link,  204 
Drive,  Hotchkiss,  218 

—  shaft,  9,  208 
Dry  cells,  105 
Dual  ignition,  158 

Electric  automobiles,  3 

—  starters,  167-183 
Engine,  9,  19,  21-48 

—  as  brake,  219 
— ,  Cadillac,  41 
--  cycles,  23 

—  cylinders,  44,  45 
— ,  Dodge,  44 

— ,  Ford,  159 

— ,  four-stroke,  23-28 

—  horse  power  of,  47 
— ,  Knight,  30 

— ,  Packard,  42 

—  speeds,  36 

— ,  two-stroke,  23 
Exhaust  gases,  22 
Explosive  mixture,  21,  22 

—  force,  22,  25 

Feed  systems,  gasoline,  56 
Fire    (gasoline),  70 
Fire  test  for  oils,  227 
Firing  order,  45 
Flash  point  of  oils,  226 
Flow  of  power,  7,  38,  39 
Flywheels,  8,  28 
Forced  feed  oiling,  233 
Ford  axle,  211 

—  cooling  system,  240 

—  engine,  159 

—  ignition  system,  133 

—  magneto,  157 


INDEX 


259 


Ford  planetary  gears,  199 

—  rear  axle,  209 

—  timer,  134 

—  transmission,  199-203 
Four-stroke  engine,  24 
Frames,  9,  14,  15 
Franklin,  air  cooling,  235 
Friction,   223 

—  clutch,  9,  11,  28,  184 
Front  axle,  13,  14,  203,  205 
Fuelizer,  Packard,  98-100 
Full  floating  rear  axle,  213 

Gasoline,  49-51 

—  and  benzol,  51 

—  carbureters,  63-103 
— ,  doped,  51 

— ,  heating  value  of,  55 

—  mixtures,    50 

—  substitutes,  49-51 

—  tanks,   56 

Gears,  differential,  10,  207 
— ,  planetary,    190,    197 
— t  progressive  sliding,  190 
— ,  selective  sliding,  190 
— ,  speed-change,  9,  12,  188 
Glycerine  for  cooling,  245 
Gravity  feed  system,  61 
Greases,  227 
Grinding  valves,  249 

Head,  detachable  cylinder,  45 
Head  lights,  182 
Heating  value  of  gasoline,  55 
High-tension  magneto,  151 
Holley  carbureters,  80 
Honeycomb  radiator,  241 
Horse  power  formulas,  47,  48 
Hot  air  connection,  83,  96 
Hot  spot  on  manifold,  95,  96 
Hot  water  connection,  86,  97 
Hotchkiss  drive,  218 
Hydrometer,  battery,  111 
— ,  Baume,  54 
— ,  specific  gravity,  54 


Idling,  86,  88 
Ignition,  104-147 

—  systems,  121,  138-147 

—  troubles,  161-166 
Insulators,  electrical,   105 
Intake  manifold,  42,  94 

—  valve,  25 

Kerosene,   244,   249 
King  bolts,  204 
Kingston  carbureter,   73 
Knight  engine,  30-31 

—  — ,  oiling,  235 

—  slide  valves,  30-31 
Knocking  in  cylinder,  52,  251 

Leaves  of  springs,  15 
L-head  cylinder,  28 
Limousine,  5 

Low-tension  magneto,  151 
Lubricants,  225 

Magnetism  and  electricity,  116 
Magneto  adjustments,  160 

—  armatures,  149 
— ,  Bosch,  156 

— ,  care  of,  160 
— ,  Dixie,  150 
— ,Ford,  157 

—  timing,  160 

—  troubles,  161-164 

Magnetos,  148-161 

— ,  high-  and  low-tension,  151 

Magnets,  demagnetized,  161 

Manifolds,  intake,  42,  94 

Marvel  carbureter,   75-76 

Master  vibrator,  135 

Mixtures,  explosive,  21,  22 

— ,rich,  101,  102 

— ,  weak  or  lean,  101 

Motors,   (See  Engines) 

— ,  starting,    (See  Starters) 

Mufflers,  10 

Multiple  disk  clutches,  186 


260 


INDEX 


Non-vibrating  induction  coil',   136, 

138 

North  East  ignition,  141 
starter,  177,  179 

Oiling,   (See  Lubrication) 
Oil  pumps,  231 
Oils,  cylinder,  226,  227 
Over-running  clutch,  172 

Packard  fuelizer,  98 

Parallel  battery  connections,  116 

Peened  piston  rings,  33 

Pistons,  22,  32,  41,  42 

Piston  displacement,  48 

—  rings,  32 

Planetary   gears,    190,   197 
Plugs,  spark,  24,  25,  119,  161,  165 
Power  diagrams,  39 
Power,  horse,  47,  48 

—  plant  suspension,  43 
Pressure  feed  systems,  61 
Primary  coil,  119 
Priming  carbureters,  69 
Progressive  sliding  gears,  190,  192 

Eadiators,  9,  240 
Eadius  rods,  217 
Kayfield  carbureter,  85 
Bear  axles,  9,  11,  206,  211 
Rectifier    alternating  current,  112, 

113 

Kemy  ignition,  145,  147 
Resistance,  electrical,  104 
Eeverse  current  cut-out,  174 

—  speed-change  gears,  191 
Eittman  process,  49 
Eoadster,  5 

S.  A.  E.  horse  power  formula,  47, 

48 
Safety  resistance,  123 

—  spark  gap,  155 
Schebler  carbureters,  82,  91 


Secondary  coil,  119 

Sedan,  5,  6 

Selective  sliding  gears,  190,  192 

Semi-floating  rear  axle,  211 

Series  battery  connections,  115 

Shafts,  cam,  26 

— ,  crank,  9,  34 

— ,  drive,  9,  208 

Shifting  gears,  13 

—  lever,  195,  197 
Shock  absorbers,  220 
Short  circuit,  105 
Slide  valves,  29-31 
Smoke  from  exhaust,  102 
Spark  advance,  125,  129,  165 

—  coil,  132,  133 

—  plugs,  24,  25,  119,  161,  163,  165 
Specific  gravity,  55 
Speed-change  gears,  9,  12,  188 
Speeds,  engine,  36 

Spiral  bevel  gears,  210 

Splash  oiling  system,  230 

Springs,  14-19 

Starter-generator,  167 

Starters,  167-183 

— ,Delco,  170,  173,  177,  179 

— ,  electric,  167-183 

— ,  Liberty  (for  Ford),  180 

— ,  North  East,  177,  179 

— ,  Westinghouse,     177,     179,     180, 

181 
Starting  in  cold  weather,  182 

—  motor  drives,   169 
— •  motor  troubles,  182 
Steam  automobiles,  2 
Steering  gear,  13,  203 

—  knuckle,  203,  228 
Stewart  carbureter,   79 

—  vacuum  feed  system,  56-60 
Stopping,  12 

Storage  battery,  106,  107 

,  charging,  107,  112,  114 

hydrometer,  111 

in  winter,  110 


INDEX 


261 


Storage  battery,  refilling  with  aeid, 

108 

— ,  sulphating,  109 
Stromberg  carbureter,  77-78 


Testing  electric  wires,  114,  115 
T-head  cylinder,  28. 
Thermostatie    cooling    system,    237 
Thermo-syphon  cooling,  238 
Three  point  motor  support,  43 
Third  brush  regulation,  176 
Tillotson  carbureter,  89 
Timers,  129 
Timing,  magneto,  160 
Tires,  10,  206,  208 
Torque  members,  217 
Transmission  gears,  13,  188 

(See  also  Speed-change  gears) 
— ,  planetary,  190,  197 
Two-cycle  engines,  23 
Two-stroke  engines,  23 
Two  unit  starting  system,  179 

Universal  joints,  13,  214 


Vacuum  gasoline  feed,  56-60 
Valve  stems,  26 

—  -in-the-head,  29 
Valves,  adjustment  of,  253 
— ,  arrangement  of,  28 

— ,  grinding,  249 

— ,  Knight  sliding,  30 

— ,  needle,  71 

— ,  timing,  253 

Vibrating  induction  coil,  127,  131 

Vibrator,  127,  135 

Volt,  definition  of,  104 

Voltage,  constant,  180 

Voltage  of  dry  cell,  105 

—  of  spark,  119 

—  storage  cell,  175 

Water-cooling  systems,  236 
Westinghouse  ignition  system,  143 

—  starters,  177,  179,  180,  182 
Wheel  alignment,  205 
Winter  cooling  solutions,  243 
Worm  differential  gear,  210 
Worm  steering  gear,  203,  205 

Zenith  carbureter,  87. 


18 


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